Strange RPG loop

Hello. I got a nice problem with an RPG program.

Somtetimes (it is not very clear why) this program goes into a tight loop.
As usual, i open a STRSRVJOB/STRDBG to check why it goes in loop, and this
isi the strange: there's no loop in program !!!

Here is the code snippet:

1201 043600 C IF *IN(02)
1202 043700 C Z-ADD 12 Z
1203 043800 C EXSR MUOVETG
1204 043900 C EXSR PREPCD
1205 044000 c Eval *in02 = *off
1206 044100 C LEAVE
1207 044200 C ENDIF

the program loops between spec 439 and 441.

Looking by debugger with F10, when the program do the leave at 441, it
reaches the end of the subroutine (which is immediatly after the ENDDO) end
the calling SR, then came back directly into spec 439 and redo the tour.

I've tried to recompile the object, (we're at 5.3.0, with recent PTF) but
it still does it. Program is very 'old-fashion' written originally in
RPGIII, Convertet to RPGLE and have some minor manteinance.

Any hint on what i can check for??? i've lloked through the whole source,
but cannot realize why there should be a similar behavior.

Thanks

--

Nicola Brion
Tech Fossil (Often called a Dinosaur) - ancient animal that make things to
work.