Increase MAX_FRAME_SIZE by 4 bytes

It's the safest fix for now to fix region scoped messages from being
dropped early

src/helpers/BaseSerialInterface.h

@@ -2,7 +2,7 @@
 
 #include <Arduino.h>
 
-#define MAX_FRAME_SIZE  172
+#define MAX_FRAME_SIZE  176   // +4 for transport codes (region scoping)
 
 class BaseSerialInterface {
 protected: