Yippie! I solved the issue.
Short version: Issue was caused by overheating due to inadequate thermal design of the FT5 electronics case.
I got new rails and out of two rails and 4 bearing cartridges I found two that were easy sliding and smoooooooooooooooooth.
Put it back together and fired of a print to find this:
Perfect printing until it failed again after 3 hours or so. What the heck? The quality was great until it went bad.
So I started digging deep the following day and did the following based on everyone's input and any possible hunches I had:
Checked speed on print g-code on SD card. Failure occurred in slow moving stack layer but layer 1 was slow too so probably not it.
Verified card is FAT32. Fan cooler file is 8M and the largest thing on the card, but failure was in random height locations so probably not card.
Checked the wiring harness. No real resistance, wired properly.
Checked resistance of steppers on Y, they are about 2.5ohms on each coil, no dead spots. (mental note I need a new DVM)
Dropped belts and rechecked rails. Did I mention they were smooooth, yeah, still smooth.
Ok, so I did everything I could here, next would be the stepper driver. Y was still at the same voltage, but maybe the motors need more Voltage? Maybe PS going bad? So I left the back cover off so I could test voltage and started the fancooler print. A few layers into the print and I see this:
Layer shifting from get go. Ok this is great, this I can work with. Well what changed? Cover is off so the tiny thermal fan under the case is probably not doing squat. Hmmm, it's probably overheating.
I put a $6 pink wallmart fan facing the open cavity, hit print and went to sleep:
And then another 4 hour print just to verify this is the problem:
It's not Tuesday but these are Taco holders.
The print quality is nice too. At 80mm max this is how nice it ends up:
I'm not a pro, but I think this is nice.
I have ordered some replacement drivers, but will leave the existing one in until I have more problems. I have ordered an 80mm fan that will be mounted in the back of the printer right at driver level, after I cut a hole in the back cover. Then retest, and once it works move on to make a cabinet etc for the printer and a dust cover.
So a question for all of you is this. Is the voltage on the driver set too high? Are we outside of the drivers capabilities for the Y axis?