diff --git a/docs/html/config_services.html b/docs/html/config_services.html
index 7975687e..d48355cc 100644
--- a/docs/html/config_services.html
+++ b/docs/html/config_services.html
@@ -51,6 +51,17 @@
 		<dt>Pref. CA PID
 		<dd>The Preferred Conditional Access Packet Identifier. Used for decrypting scrambled streams.
 
+		<dt>Lock Pref. CA PID
+		<dd>The locking mechanism selection for The Preferred Conditional Access Packet Identifier.
+		<dl>
+		   <dt>Off
+		   <dd>Automatic Preferred Conditional Access Packet Identifier selection.
+		   <dt>On
+		   <dd>Keep Preferred Conditional Access Packet Identifier selection (no automatic modifications allowed).
+		   <dt>Only Pref. CA PID
+		   <dd>Filter mode - use only Preferred Conditional Access Packet Identifier for the streams decryption.
+		</dl>
+
 		<dt>Character Set
 		<dd>The character encoding for this service (e.g. UTF-8).
 
diff --git a/src/descrambler/capmt.c b/src/descrambler/capmt.c
index e60ce7a4..babd1a81 100644
--- a/src/descrambler/capmt.c
+++ b/src/descrambler/capmt.c
@@ -1530,6 +1530,9 @@ capmt_caid_change(th_descrambler_t *td)
   lock_assert(&t->s_stream_mutex);
 
   TAILQ_FOREACH(st, &t->s_filt_components, es_filt_link) {
+    if (t->s_dvb_prefcapid_lock == 2 &&
+        t->s_dvb_prefcapid != st->es_pid)
+      continue;
     LIST_FOREACH(c, &st->es_caids, link) {
       /* search ecmpid in list */
       LIST_FOREACH(cce, &ct->ct_caid_ecm, cce_link)
@@ -1809,6 +1812,9 @@ capmt_service_start(service_t *s)
     pthread_mutex_lock(&t->s_stream_mutex);
     TAILQ_FOREACH(st, &t->s_filt_components, es_filt_link) {
       caid_t *c;
+      if (t->s_dvb_prefcapid_lock == 2 &&
+          t->s_dvb_prefcapid != st->es_pid)
+        continue;
       LIST_FOREACH(c, &st->es_caids, link) {
         if(c == NULL || c->use == 0)
           continue;
diff --git a/src/descrambler/cwc.c b/src/descrambler/cwc.c
index 36d70cea..af9f64c4 100755
--- a/src/descrambler/cwc.c
+++ b/src/descrambler/cwc.c
@@ -101,6 +101,7 @@ typedef struct ecm_section {
   uint16_t es_seq;
   char es_nok;
   char es_pending;
+  char es_resolved;
   int64_t es_time;  // time request was sent
   size_t es_ecmsize;
   uint8_t es_ecm[4070];
@@ -711,10 +712,12 @@ handle_ecm_reply(cwc_service_t *ct, ecm_section_t *es, uint8_t *msg,
 {
   mpegts_service_t *t = (mpegts_service_t *)ct->td_service;
   th_descrambler_t *td;
-  ecm_pid_t *ep, *epn;
+  ecm_pid_t *ep;
+  ecm_section_t *es2;
   char chaninfo[32];
-  int i;
+  int i, j;
   int64_t delay = (getmonoclock() - es->es_time) / 1000LL; // in ms
+
   es->es_pending = 0;
 
   snprintf(chaninfo, sizeof(chaninfo), " (PID %d)", es->es_channel);
@@ -749,17 +752,20 @@ handle_ecm_reply(cwc_service_t *ct, ecm_section_t *es, uint8_t *msg,
 	   "Req delay: %"PRId64" ms)", t->s_dvb_svcname, chaninfo, seq, delay);
 
 forbid:
+    j = 0;
     LIST_FOREACH(ep, &ct->cs_pids, ep_link) {
-      for(i = 0; i <= ep->ep_last_section; i++)
-	if(ep->ep_sections[i] == NULL) {
-          if(es->es_nok < 2) /* only first hit is allowed */
-            return;
-	} else {
-          if(ep->ep_sections[i]->es_pending ||
-	     ep->ep_sections[i]->es_nok == 0)
+      for(i = 0; i <= ep->ep_last_section; i++) {
+        es2 = ep->ep_sections[i];
+        if(es2 && es2 != es && es2->es_nok == 0) {
+          if (es2->es_pending)
 	    return;
+          j++;
         }
+      }
     }
+    if (j && es->es_nok < 2) /* only first hit is allowed */
+      return;
+    
     tvhlog(LOG_ERR, "cwc",
 	   "Can not descramble service \"%s\", access denied (seqno: %d "
 	   "Req delay: %"PRId64" ms) from %s",
@@ -776,7 +782,9 @@ forbid:
     ct->cs_channel = es->es_channel;
     ct->ecm_state = ECM_VALID;
 
-    if(t->s_dvb_prefcapid == 0 || t->s_dvb_prefcapid != ct->cs_channel) {
+    if(t->s_dvb_prefcapid == 0 ||
+       (t->s_dvb_prefcapid != ct->cs_channel &&
+        t->s_dvb_prefcapid_lock == 0)) {
       t->s_dvb_prefcapid = ct->cs_channel;
       tvhlog(LOG_DEBUG, "cwc", "Saving prefered PID %d for %s",
                                t->s_dvb_prefcapid, ct->td_nicename);
@@ -802,20 +810,13 @@ forbid:
 
     descrambler_keys((th_descrambler_t *)ct, msg + 3, msg + 3 + 8);
 
-    ep = LIST_FIRST(&ct->cs_pids);
-    while(ep != NULL) {
-      if (ct->cs_channel == ep->ep_pid) {
-        ep = LIST_NEXT(ep, ep_link);
-      }
-      else {
-        epn = LIST_NEXT(ep, ep_link);
-        for(i = 0; i < 256; i++)
-          free(ep->ep_sections[i]);
-        LIST_REMOVE(ep, ep_link);
-        tvhlog(LOG_WARNING, "cwc", "Delete ECM (PID %d) for service \"%s\" from %s",
-                                   ep->ep_pid, t->s_dvb_svcname, ct->td_nicename);
-        free(ep);
-        ep = epn;
+    LIST_FOREACH(ep, &ct->cs_pids, ep_link) {
+      for(i = 0; i < ep->ep_last_section; i++) {
+        es2 = ep->ep_sections[i];
+        if (es2) {
+          es2->es_resolved = 1;
+          es2->es_pending = 0;
+        }
       }
     }
   }
@@ -848,9 +849,19 @@ cwc_running_reply(cwc_t *cwc, uint8_t msgtype, uint8_t *msg, int len)
           for(i = 0; i <= ep->ep_last_section; i++) {
             es = ep->ep_sections[i];
             if(es != NULL) {
-              if(es->es_seq == seq && es->es_pending) {
-                handle_ecm_reply(ct, es, msg, len, seq);
-                return 0;
+              if(es->es_seq == seq) {
+                if (es->es_resolved) {
+                  mpegts_service_t *t = (mpegts_service_t *)ct->td_service;
+                  tvhlog(LOG_WARNING, "cwc",
+                         "Ignore %sECM (PID %d) for service \"%s\" from %s (seq %i)",
+                         es->es_pending ? "duplicate " : "",
+                         ep->ep_pid, t->s_dvb_svcname, ct->td_nicename, es->es_seq);
+                  return 0;
+                }
+                if (es->es_pending) {
+                  handle_ecm_reply(ct, es, msg, len, seq);
+                  return 0;
+                }
               }
             }
           }
@@ -1194,8 +1205,8 @@ cwc_thread(void *aux)
     ts.tv_nsec = 0;
 
     tvhlog(LOG_INFO, "cwc", 
-	   "%s:%i: Automatic connection attempt in in %d seconds",
-	   cwc->cwc_hostname, cwc->cwc_port, d);
+	   "%s:%i: Automatic connection attempt in %d seconds",
+	   cwc->cwc_hostname, cwc->cwc_port, d-1);
 
     pthread_cond_timedwait(&cwc_config_changed, &cwc_mutex, &ts);
   }
@@ -1735,6 +1746,7 @@ cwc_table_input(void *opaque, int pid, const uint8_t *data, int len)
       es->es_channel = channel;
       es->es_section = section;
       es->es_pending = 1;
+      es->es_resolved = 0;
       
       memcpy(es->es_ecm, data, len);
       es->es_ecmsize = len;
@@ -1980,6 +1992,9 @@ cwc_service_start(service_t *t)
     LIST_FOREACH(pcard, &cwc->cwc_cards, cs_card) {
       if (pcard->cwc_caid == 0) continue;
       TAILQ_FOREACH(st, &t->s_filt_components, es_filt_link) {
+        if (((mpegts_service_t *)t)->s_dvb_prefcapid_lock == 2 &&
+            ((mpegts_service_t *)t)->s_dvb_prefcapid != st->es_pid)
+          continue;
         LIST_FOREACH(c, &st->es_caids, link) {
           if (c->use && c->caid == pcard->cwc_caid)
             break;
diff --git a/src/input/mpegts.h b/src/input/mpegts.h
index 292d2527..791e56be 100644
--- a/src/input/mpegts.h
+++ b/src/input/mpegts.h
@@ -428,6 +428,7 @@ struct mpegts_service
   uint16_t s_dvb_servicetype;
   char    *s_dvb_charset;
   uint16_t s_dvb_prefcapid;
+  int      s_dvb_prefcapid_lock;
 
   /*
    * EIT/EPG control
diff --git a/src/input/mpegts/mpegts_service.c b/src/input/mpegts/mpegts_service.c
index ed41eaf6..e4dc026b 100644
--- a/src/input/mpegts/mpegts_service.c
+++ b/src/input/mpegts/mpegts_service.c
@@ -55,6 +55,17 @@ mpegts_service_class_get_network ( void *ptr )
   return &s;
 }
 
+static htsmsg_t *
+mpegts_service_pref_capid_lock_list ( void *o )
+{
+  static const struct strtab tab[] = {
+    { "Off",                0 },
+    { "On",                 1 },
+    { "Only Pref. CA PID",  2 },
+  };
+   return strtab2htsmsg(tab);
+}
+
 const idclass_t mpegts_service_class =
 {
   .ic_super      = &service_class,
@@ -133,6 +144,14 @@ const idclass_t mpegts_service_class =
       .off      = offsetof(mpegts_service_t, s_dvb_prefcapid),
       .opts     = PO_ADVANCED,
     },
+    {
+      .type     = PT_INT,
+      .id       = "prefcapid_lock",
+      .name     = "Lock Pref. CA PID",
+      .off      = offsetof(mpegts_service_t, s_dvb_prefcapid_lock),
+      .opts     = PO_ADVANCED,
+      .list     = mpegts_service_pref_capid_lock_list,
+    },
     {},
   }
 };
diff --git a/src/service.c b/src/service.c
index 65be059f..d1d1dcfb 100644
--- a/src/service.c
+++ b/src/service.c
@@ -405,9 +405,9 @@ filter:
           ca = NULL;
           if ((esf->esf_caid != (uint16_t)-1 || esf->esf_caprovider != -1)) {
             LIST_FOREACH(ca, &st->es_caids, link) {
-              if (esf->esf_caid != -1 && ca->caid != esf->esf_caid)
+              if (esf->esf_caid != (uint16_t)-1 && ca->caid != esf->esf_caid)
                 continue;
-              if (esf->esf_caprovider != -1 && ca->providerid != esf->esf_caprovider)
+              if (esf->esf_caprovider != (uint32_t)-1 && ca->providerid != esf->esf_caprovider)
                 continue;
               break;
             }