That is what I could find.
SRCVLF is the block from library MAKMP5. In the help to this FB it is written that it consist of combination of CBRM/CBT blocks (this blocks are inside SRCVLF). CBRM/CBT are from library fba121, so as you have help-file for fba121 you may read about how this combination works under description of CBRM block. May be this will help you to eliminate the error.