First let me quickly give a thank you to all techs and wannabe-techs and plain old hobbyists on here, I've been following for a while now and this is an invaluable resource!

I have two machines with different issues, and was wondering if anyone would throw a new guy a bone.

GR3750: Got it about 6 mos ago, hasn't been able to dispose of any master, regardless of drum, since I got it. Thinking it may be the vertical transport roller motor, but unsure. Recently I've also been getting Paper Feed Jam errors. Lots of floating registration so I assume the timing is off, more on that later.

GR3770: Just got this machine TODAY. Was working well when I tried it out in it's former home in a print shop, and when I brought it into my studio it performed decently well - that is until I started to experience the same problem with cadence that I am with the 3750. With a manual in hand I decided both of the old machines probably have P-discs that are out of whack and went to work adjusting the 3770, following carefully the instructions of the tech manual.
As soon as I began printing again, maybe 10 copies in, there was a paper jam under the drum, and the paper wouldn't give way when I tried to pull it out from the exit side. The fan that activates while running copies let out a sustained whirr and wouldn't stop. I tried to remove the drum, and it wouldn't release from the machine. I used what the manual drum lock release on the bottom right of drum unit to pull (kind of force) it out. Then I turned the machine off, did a hard reset on restart, and my pressure roller got stuck in a position that will not allow any drum to enter the machine...

What is going on here? Did I totally screw up the timing of the whole machine with that P-disc adjustment?
I was planning on also going ahead and adjusting the P-disc on the 3750, but I'm afraid the same thing will happen. The Cam alignment slots are on for both cam pulleys and discs, and I adjusted the notch

Please advise... I'm in a bad way!