Yes, on my 2188 had the same problem, i have changed the spring to a heavier one. That was 4 years ago and still on the same belt, aprox. 800 hrs. As for the bearings i can't help you much,sorry.
We never had much trouble with the rotor belt on our 1680 until last year. It pulled two brand new ones in two in a couple days. The problem was the PTFE lined bearing inside the sheave which slides on the chromed stub shaft. It is lock-tighted in place, and it came loose some how which kept the sheave from sliding free enough. That extra friction is just like having a weaker spring. I would suggest taking the whole torque sensor unit off the machine and tearing it completely down in the shop. See how much friction you have on the PTFE bearing. If you need to you can hand polish the PTFE with very fine paper until it slides freely. Here's a link to the bearing style I'm talking about.