I tried this once. One of the amps was a SE-OTL amp and the other (if I recall) was a solid state.
Long story short, I sometimes switched between amps turning one off and the other on (and maybe back/forth) I never had them both on at same time. I used an A/B switch and they were wired to same speaker.
Discovered that if I turned the SS amp off and the OTL on, all was fine. If however, I had the OTL amp on and switched over to the SS amp, the SS amp would go into protection mode and reset.
Turns out the OTL amp discharged a tiny tiny amount of DC current. This current typically went from the RCA inputs, back to the preamp where nothing happened.
Since it was being "shared" electronically with the other amp via the "Y" cord, the DC current went to the SS amp and pushed it into protection mode.
This subject is beyond my technical expertise, I'm simply relating a story of what happened to me under a similar circumstance.