VAXELN HELP!! needed

VAXELN is new to me, but I am reasonably at home in the internals of RSX11M, MTS and OS 360. I was called in by the application programmer when he encountered a somewhat deep problem. One or two times a month in the 3rd of three RT1000 running V4.0 of VAXELN the two communications tasks with the microVax 3300 running VMS 5.2 stop. One with access violation, reason mask 05 and one with access violation or with a kernel stack not valid exception. These tasks are identical and each serves its own sorting unit. The VAXELN systems use the DDCMP_V2 module. The systems run continuously. The stop address is for both tasks always in the DAP module (from june 7 1989) at 1FFC from the start It looks as if the FP register contains 0 during the last CLRB -4C4(FP) intruction.I conclude this from the virtual address =FFFFFB3C message.. The system stopped at the same location during startup earlier in the project each time when the 3rd realtime vax was started, but then:maximum links was 32 and maximum circuits was16. This error disappeared when these quantities were doubled to maximum links=64 and maximum circuits=32. The earlier values were ok during the years when only two realtime vaxes were active.and with 2 realtime vaxes these crashes were not noticed. The realtime vaxes all have the remote debugger. The installation is 140 km from my home. It looks as if register information is hard to get at. Suggestions? Has anyone encountered a similar error? Who has suggestions?. When this gets highly detailed contact off list might be best.