Sequential circuits samplers

i have a Prophet 3000 Rev B with 4 megs of ram.  i replaced the LCD screen with a blue 
backlit screen which looks great.  if anyone needs info on this mod i'd be happy to help out.

my pk3 has a couple of issues and i was wondering if anybody could help out.  

the first problem is that as the unit plays through the voices, each voice seems to have a 
slightly different filter setting.  it's most noticable when i turn the resonance up so the filters 
self oscillate.  i can very clearly hear the pitch of the self oscillation changing as i step 
through the voices.  any ideas what might be causing this?

the other issue occurs when i play drum sounds with a sharp attack.  the attack sounds 
different each time the sound is triggered.  it almost sounds like it's sometimes clipping the 
circuit and sometimes it's not, though i'm quite sure the sound is not clipping at all.  

i'm very familiar with the unit and have ruled out the possibilty of user settings for both 
issues.  i'm almost resigned to sending it to wine country but wanted to check here first.

thanks

nick