Talked with SBC today, mainly to diagnose the issue. There are several possibilities (some related to age/mileage of the truck): bad pilot bearing, bad input bearing, worn pivot points on the fork, and a warped clutch disc. They want it disassembled to find the issue. I had it to the install place last spring, and they saw the issue I was describing. The warped disc can be caused from slipping the clutch. Of all those possible issues (short of something new developing) everything was replaced and. there was no indications of impending issues... I guess it came on so quick that I don't think it could be a "wear" issue, such as bearings.
And for the record, (the best I can remember) the issue started sometime after a 3rd gear start to merge into rush hour traffic (the NV5600 and 4. 10s is a slow combo). At least that's the only time I could point to that was out of the "ordinary daily drive" that week. I don't remember slipping the clutch, but slipping seems to be the main cause of an OFe warping. But I guess the main question is how much slipping is harmful? I always thought some slippage was expected, and perceived "slipping the clutch" as riding it such as in drag racing or just letting it slip uncontrolled (overcoming the friction). I mean, you got to slip a clutch some to do any maneuvering, such as for a trailer as an example. So how much is considered normal?
So who knows what they will find... I may be buying a clutch, among other things. If it comes to that, I may just sell the truck and try something else (as in another brand). I do feel bad as I told them it happened in stock configuration, but later remembered the entire reason I needed a clutch was because of my SmartyJR slipping my faulty OE clutch (which had over 180k on it at that point, so its not like i am hard on a clutch).
They did indicate the OFe has been redesigned, and the Fe side is now multiple pieces instead of a solid disc to address potential warping.