Any known issues with Dell computers and ISA bus functionality?

I've got a 16-bit ISA card (part of a specialty piece of data
acquisition equipment) that I know works in several different
mainstream motherboards.

It doesn't function correctly in a computer that I've been asked to
test it on:

Dell optiplex gx150 manufactured April 2002.

This is a desktop tower computer with one 16-bit ISA bus slot that is
connected to the motherboard via a side-mounted edgecard connector (as
if the ISA slot was designed as an optional add-on component to the
motherboard).

While debugging this board with a scope and some machine code written
and executed from within the DOS debug program, it seems that the
motherboard is not correctly honoring the IOCS-16 bus signal being
generated by the ISA card.

I think it's generating two 8-bit writes in response to a 16-bit I/O
write. The IOCS-16 signal seems to be working correctly.

Are there any known issues with Dell computers like this and ISA bus
functionality?