I just put this in another thread but...........
The Indivision ECS is picky about clean power. On my A500+ I switched from a Obese Boy power supply (not very politically correct name) to a modded XT power supply. It was like magic the Indivision started working without a problem.
I got the old Oscope out and looked at the Obese Boy supply, the 5 volt line was a bit noisy particularly when the floppy drive it being accessed. Before the power supply switch I had all types of issues with the Indivision. It would everything from drop signal to have tearing screen issues.