You could delete/rename your Fvwm-Start(configuration)-file.
mv ~/.fvwm/.fvwm2rc ~/.fvwm/.fvwm2rc-old
Then Fvwm should start “clean” without special banner-settings or without trying to run xmodmap.sh
If this works, you can create an empty .fvwm2rc with an editor, and start copying lines from your .fvwmrc-old to the new one.
Like this you can find out the “wrong” entry.
Or you use a .fvwm2rc from this forum (Screenshots and Configs).
Mark