I had a space jam with that sort of high pitched crackling sound but it only happened when the Tasmanian devil sequences appeared,. That turned out to be a faulty rom .(think U18 rings a bell) It was Something to do with if the sound roms were downloaded from the pinball free site there was a software problem with that site for that machine .I had to buy the roms from Rompingirl (find this guy on ebay) fault cured. As for your wabbit hole problem Cliffy (passion for pinball) did not make protectors for space jam when i owned one (he may now )well worth asking him Great Chap to talk to. There was a guy in Portugal made wabbitt hole protectors (again on ebay) (they were a bit thick if i recall correctly) and you had to really mess around altering the curved scoop at the back of the hole to get the ball to go into the hole every shot. Hope this helps
cheers Keith (UK)

For your sound issue I just fixed mine. You need to update Rom U36. But if you download the regular version from IPDB it won't work and will have the cracklin' sounds. You need to download the PinMame Version and burn u36 and replace it in your game. That will fix your issue.
I don't have a cliffy on mine but I can see how that would cause a problem. Either adjust the deflector plate, build up a couple layers of mylar in front of the cliffy edge, or take off the cliffy.