I am occasionally getting an IO ERROR when executing commands, even when I successfully executed other commands before it gave me the error. If I check the kernel using CLOSED APPLE+CONTROL+RESET, it gives me the error message "IOU FLAG E5:1". If I check the kernel using the same method before the IO ERROR message appears in the console, the diagnostics tool tells me KERNEL OK.
To add to the confusion, after I run into the IOU FLAG error, if I reset the computer using OPEN APPLE+CONTROL+RESET, the drive cannot recognize the disk, spinning endlessly. In order to fix it, I have to take the disk out (after stopping the drive) and manually rotate the disk so that the index hole is visible. This manual fix also allows me to use commands after the IO ERROR message is shown (if I try without the fix it displays the error again. I have found this out from trial-and-error)
To make my and your brain hurt further though, the drive is very random. It can go for a long time without me needing to manual fix it, but all of a sudden it wants to be handheld by rotating the disk as stated in the paragraph above. I could not make a pattern out of this no matter how long I stared at the screen.
All of the above makes me think it is a drive issue (I have two Disk II's). If so, can anyone tell me what's wrong and tell me how to fix this or point me to resources that show me how to correctly fix this? I am a relatively new to vintage computing and have done maintenance on the Mac 128k internal floppy drive.