🚀 go-pugleaf

I have an interesting problem with my XT, and hope that the
net can provide some suggestions as to how to proceed.

The floppy drive on my XT occasionally refuses to read certain
files.  The error message varies, but occasionally includes
"DRIVE NOT READY - CLOSE DOOR" etc.

I wrote a program to read the file a sector at a time, and
received no error.  (i.e. The program asks DOS to read the
next 512 bytes.)

However, when the program asks DOS to read several sectors at once
(i.e. a single DOS request for more than 512 bytes at once)
the error occurs.

I suspected timing problems, so I checked the drive's speed and found it
accurate.  I suspected alignment problems (as the files were written on
another machine) but the disk works fine on other machines, and my
computer reads the DOS master, Diagnostics, etc correctly (most of the
time).

Why would a single-sector read and a multi-sector read produce different
results?

(I can always just replace the drive, but I really am more interested in
reason(s) and speculation(s) as to why.)

Many thanks,
kpk