Try these:
mmu=yes
warp3d=yes
force=1
voodooint=yes
Switch rtg.library 40.3994 --> 40.3992 (
Picasso96-2_1.c.zip), the newer one can cause problems with real amigas. You could also check if the other libraries are upto date.
Kinda running out of suggestions as I don't have an A4000 - anyone that could help with this?