I have killed a Floppy drive by unplugging the power (data was connected) while the PC was still on.
Just as a reminder to not do this. 😁

With those symptoms, the I/O controller card is the primary suspect. I assume no poltergeist changed the jumper settings on the I/O card last night, so given the current issues, the card might just be broken. So you have a different I/O controller card you could try? Generally, I/O controller cards are interchangable between 286, 386 and 486 computers. If the 486 computer has a VL-based I/O controller card, just the hard drive is on the VL bus, and all other stuff is ISA connected. So floppy, serial, parallel and game port on a VL controller card work in 286-class and 386-class computers. Even 8-bit XT I/O cards work newer computers, but they do not include a hard disk interface.

Well that was a lesson in FDD shehhanigans. I had three FDD drives and 7 disks. 2 drive was faulty and several disks. I was trying good disks with the faulty drive and bad disks in the good two. Only thing I can think of.

Anyway suddenly all is good. I have checked for dry joints on the card (been taking it out a few times) but seems to be ok now. Old hardware = fun times.