Help on DIVIDE 57c and ESXDOS

Hello to all!
I have a question for some expert : i own an old DIVIDE 57c, working good.
And i have two Speccy ,a  gummy rev 3 and a PLUS with rev 6a.
On the 6a DIVIDE works with all "firmwares", included ESXDOS.
On the rev 3 DIVIDE works perfect with fatware or other firmwares but NOT with the ESXDOS (not boot and weird things happen, blocks on video, reset, etc..etcc..) What can be the reason ?
Tried all versions , from old 7.x to las 0.89 : same not working with the rev 3 !
Not a big problem because i can use fatware .14 for loading games but i dont'understant the cause.
Both 48k speccy tested for ram faults. Both working perfect with IF1+microdrive+ joy interface...
Both loading well tapes, sound and all, so ULA seems ok.
I repeat fatware or others divide firmware are working also on the rev 3 speccy...
Strange ?
THANKS !

PS: i add that divide is working good also on my 128+2 with esxdos...