Hi, I have an AT clone 80286 motherboard with an integrated floppy controller that, very recently, has been acting very strange. When I boot up the system it will detect both drives and they will perform a head-seek without issue. It will (sometimes) boot from a 720k disk and very rarely from a 1.44m disk, seems to be random as to whether or not it will each time. Other times it will fail to boot and just send me into BIOS or occasionally freeze. The system ROM has some built-in floppy tests and when running those it will sometimes work; again, it works more often on 720k and 360k disks than 1.44m (I don't have any 1.2m disks to test). However, oftentimes it will give CRC errors at random places on the disk, and sometimes it will fail to read, format, or write the disk in any capacity just giving "Disk Error Unknown" Exactly what (and when) happens is different every time and rarely it will actually work normally for a while.

I have deduced that it is a controller problem since both of the drives are fine in other systems and when I used an addin card's floppy controller (and disabled the integrated one) everything worked fine. I have tried running the system at both 6mhz and 12.5mhz, same behaviour at either speed. I know that the easy solution would be to just use the addin floppy controller but that isn't really an option long-term since I plan to use basically all the ISA slots. Does anybody know what the issue may be causing this seemingly random instability of the FDC? Or where to start troubleshooting the problem.

The motherboard is "ITT Motherboard" from an ITT Xtra Professional series/400 computer. Here is a picture of the board of with the floppy controller region circled:

Note: the floppy controller has been working fine until recently when I was going to install an MFM controller and at a certain point the system stopped booting from floppies and the issues as described started happening; a little later, for a while the whole board seem bricked (no POST, beep, or display) but, after some cleaning, it randomly started working again and Supersoft/Landmark ROMs didn't seem to find any issues. (I attached an image of Landmark ROM running, FDC was not enabled when I ran this) The main system is working fine now but the issues with the integrated FDC have persisted.