diff --git a/documentation/clients/GTFPGA.md b/documentation/clients/GTFPGA.md
index b89a6c419..4352e515d 100644
--- a/documentation/clients/GTFPGA.md
+++ b/documentation/clients/GTFPGA.md
@@ -1,7 +1,5 @@
 # GTFPGA {#gtfpga}
 
-@defgroup gtfpga GTFPGA
-
 The GTFPGA card is an extension card for simulator racks from RTDS.
 The manufacturer provides a VHDL module to exchange data via fiber optics between the GTFPGA and GPC cards.
 
diff --git a/documentation/clients/OPAL.md b/documentation/clients/OPAL.md
index bd78c0234..0a03cc71f 100644
--- a/documentation/clients/OPAL.md
+++ b/documentation/clients/OPAL.md
@@ -1,7 +1,5 @@
 # OPAL-RT {#opal}
 
-@defgroup opal OPAL-RT
-
 The communication between OPAL-RT models and the S2SS is established by using ansychronous programs.
 Asynchronous programs are are a feature of RT-LAB. They are used to exchange data between Simulink models and custom C programs.
 
diff --git a/documentation/figures/msg_format.dia b/documentation/figures/msg_format.dia
index 996e0a5a9..4914c7b75 100644
Binary files a/documentation/figures/msg_format.dia and b/documentation/figures/msg_format.dia differ