[Coco] Problem with disk controller in the MPI

[Charles J Pelosi]

I'm having an issue with a Multi-pak 26-3124.
Occasionally when I turn on the coco the disk system doesn't work properly.
It is a two drive system with a FD-501 controller in the MPI. Both disk drive activity lights turn on and the drives are not usable.
If I turn it all off and wiggle the disk controller a little it will work again when I turn it back on.
It seems to do this with all disk controllers I own. I've tried them in slot 3 and 4. Same result.
The only other pak being used is the sound/speech pak.
I have cleaned all card edges and the MPI slots / switches. Pink eraser, alcohol, electronic spray, deoxit.
Also tried another power supply from a loose MPI case / power supply I have laying around.
Nothing seems to help besides to wiggle the disk controller. It just seems odd to behave the same in slot 3 and 4.
Any advise on how to get this device working more reliably? When it does not have this problem the coco functions great with it.
Thanks for reading!

Charles