I believe I have found the root cause of the issue. as others above posted my TPU always jammed at the top of the heat break. I found the top of my heat break had a very sharp edge. It seems as the TPU was pushed through it would bulge just a bit at the top of the heat break and the sharp edge slowly gathered filament until the extruder could not push it through any longer. I sanded the end of the heat break down a few tenths of a mm with 320 and then smoothed it out with some 2000 so there is no longer a sharp edge. I didn't take a picture of it before I sanded it, but this is basically what it looked like. Here it is after I removed the sharp edge. You can see there is a small defect on the far side of the opening. this is from the extruder gears rubbing on the top of the heat break. Here it is installed after I sanded it. It is still very tight to the extruder gear but the edge of the heat break no longer catches the filament. I could not get more than 30 minutes of printing TPU complete prior to my modification, but I just finished a 2.5 hour test print and had no issues. I used Sainsmart TPU at 30mm/s, 215, 0.5mm retracts, which were my normal TPU settings on the previous stock hot end/extruder. Printer is a monoprice maker select V2. I just purchased a Hemera Revo for another printer, and the nozzle/heat break combo does not have a sharp edge like my original hemera did. I am hoping someone else with this issue can inspect their heat break and see if it has a sharp edge like mine did.