I recently experienced something similar on a real Easyflash cartridge. The game did report that the save did fail, when trying again, the game did crash. Luckily I made a backup on floppy, but still, a few hours of gameplay are lost.
Viewing post in Briley Witch Chronicles (C64) comments
I have uploaded my savegame here: http://www.freepascal.org/~daniel/brileysave.zip