Have you tried the various pull-up fixes that exxos has posted elsewhere (I will try & find the thread if it's not clear which one I mean, possibly one about mandatory fixes) - I think that there was something relating to (missing?) resistors on the original design & having to fit some (or change the values) when replacing the original floppy with another...
It's a good few months since I first read it, so I may have mis-remembered some of the details (old age seems to be affecting my memory nowadays
)Edit: See below for the databus pull-ups to helpwith DMA to HDD & FDD/Ultrasatan etc.
https://www.exxosforum.co.uk/forum/viewt ... xes#p27505