Hi Bernie - welcome to the forum! (Too bad you couldn't have started with an easy question, like "how do I get the system time?")
I vaguely recall a symptom like this prior to 5.0, relating to PolyShell and/or changing the terminal driver from within A-Shell. The problem wasn't particularly serious, because the fact that the message is seen indicates that the error was trapped, and since it occurred on exit, everything was being cleaned up anyway.
If the memory fault occurred within A-Shell's process space, it would be trapped by A-Shell and a copy of the current log file, called
core would be in the directory where the miame.ini is found (i.e.
ls -l /vm/miame/core*) But in that case, if you saw any message, it would probably be "segmentation fault". I believe that "memory fault" is the message output by the bash or korn shell when it detects a segmentation fault. In the case of the terminal driver change, the issue had to do with both processes (the outer login shell and A-Shell) sharing the environment variable space, and when A-Shell relocated the TERM environment variable, it left the outer shell with an invalid pointer to that variable when A-Shell exited. If that's the problem, then I believe it was fixed quite awhile ago.
Even if that's not the issue, I would strongly urge updating to at least 5.0, and preferably 5.1, since it is next to impossible now to investigate such problems and provide patches for versions older than 5.0.
As an aside, if your users are seeing this message on exit from A-Shell, that implies that when they exit from A-Shell, they end up at the Linux shell prompt, rather than closing the session and closing the telnet window. That might be appropriate for administrators who need access to the Linux shell, but probably is not appropriate for ordinary users. To eliminate that, you can insert an "exit" command after the "ashell..." launch command in the $HOME/.bash_profile (which is typically how A-Shell gets launched). Or you could insert an "exec" at the start of the of "ashell..." command line (to replace the Linux shell entirely with A-Shell, which would also probably eliminate any possibility of there being a shared memory conflict between A-Shell and the Linux shell, since there would be no Linux shell left.)
Also, although this may seem like a "cover up", if your telnet session is going to be terminated when you log out of A-Shell (i.e. "host"), then perhaps you should have the telnet window automatically close at the same time. In the case of ZTERM, there is a "close on telnet close" option in the Configuration>Options dialog.