S5 endless loop

We have a 135U with 928b cpu controlling a 9 MW condensing turbine.
I am in the process of working out what is happening with various problems with the machine/program. We are having the documentation translated and I have(expecting delivery)copy of bergers 135u book

I am using S5 for windows and when i use the simulator to run the program an error message pops up telling me that "Block FB 196 may have an endless loop" and am unable to progress further.
the block in questions code: NAME : Stop
ANF : STP
JU =ANF
BE
It does look like an endless loop and is called by OB's 21 22.
The program runs on thge real PLC but appears a little glichy.
I'd be interested on comments on how the start and reset OB's use this FB 196 .

My suggestion is that the only type of restart that is allowed for your system is a cold restart (OB20). If a warm restart is attempted, FB196 gets called and goes into the endless loop preventing any further processing from taking place.