To duplicate: set ASCII only graphical mode as default on the NotEye settings, then restart ADOM. Use monster memory.

Results in error message:
NotEye script has crashed
error: did not yield [./games/adom.noe:433: attempt to index global 'M' (a nil value)]

You can still continue playing after this; just can't use monster memory.
Swithing graphical mode to tile mode removes the issue, even if you switch back to ASCII only.