i think that i searched for it and didn't found any #BCCE, but maybe i didn't look well, but this doesn't make sense since the save/load works on the M4 (not always for me)
True, but it also doesn't use BCCB, so that explains it.
And another quick test with WinAPE, fill the memory below AMSDOS worksspace with some random bytes (-128+4 would be M4 rom workspace)... I don't see anything overwriting it when in the load/save dialog, before starting the actual game.
But when I start the game, this gets overwritten. So its using the himem upto AMSDOS workspace.
So if your hangs has to do with entering the game and going back, then load/Save stuff again, this is probably it.
How to fix ? - don't init amsdos and only M4 dos, then you will have no himem conflict.