I dont know if you've already had a look for things to fix it but i found this when reading up about the GVP Specturm 24 "
does not work reliably with Buster rev. 9" which you state that you have. Found it here at the
Amiga Hardware Database.
Afraid I dont have a 3k or 4k to swap but good luck. That and i live in the UK! :-D
