Need Help Brothers Mutoh and his cousin Westcomp D30

Back again. I'm sure some of you might know about my issues I've been having. First, I inherited an ancient system, and a Mutoh Valuejet 1604A and SC-1400D cutter. I'm sort of baffled about this issue I'm having with the SC-1400D. I haven't used it much lately since it been doing this, and brought in another vinyl cutter I found covered back in the shop. But the SC-1400D it will start cutting vinyl and when it's finished, I find some of the cuts are visible on the surface of the vinyl, but it doesn't cut all the way through the vinyl to be able to weed it out. Even after a perfect test cut. But in the same file it will take certain letters that don't cut through the vinyl and the next letter it will cut through the vinyl and backing. It's strange. I had to hand cut the "uncut" letter and pick up off the floor the other letters and tape them into place before masking off. I cannot figure it out. I have gone through the menu and check everything i can think of to fix the issue. Which is why I brought out this old cutter I found in the back.
The Westcomp D-30 looks just like my Summa D-610. Menus is only slightly different. So I thought kool. This will work until I can get the Mutoh straight. Wrong. Now i know why that one was retired too. Anything over 2 feet in length, the tracking seems off and it will move over the course of shuffling the vinyl back and forth during the cut. Causing it to shuffle off the left wheel guide and of course gets jammed in the machine. I'm having to send sections of a job thru and watch it very closely. It moves the vinyl to the right everytime. Not sure what the deal is with that either.
So I have brought in my personal Summa cutter to handle any cut jobs going on right now. The equipment here is ancient, and we really do need to look at updating our printer and cutter system. But until we do, I need these working the best they can.
Is there a remedy for the 2 afflictions on these cutters? Any input would be greatly appreciated. Pulling my hair out!