Same problem here. Having a fair number of old hardware synths, the midi device panels are important to me. In fact it is one of the main reason for choosing the pro version of Cubase. Quite surprised that the bug exists because nothing has changed in the device panel part of Cubase for many many years so I am sure the source code for it is untouched. They probably use some newer XML library that can’t read their own xml files.
I would actually love if they brought the device panels into the 21st century since it all looks and feels very old-skool.
Anyway, the bug is probably (hopefully!) already on Steinberg’s fix list but I have created a support ticked for the issue anyway. Fingers crossed this is fixed in 9.02