Originally Posted by
sschick
I had similar tension issues on my 99K . It turned out that the shaft where the tension discs sit was loose. I just tightened it up and the tension has been fine ever since. I don't have a featherweight so I don't know what the tension disc assembly looks like or how it is assembled, but it might be something to look at.
Shari
Since you've had it in to be serviced without much improvement. I'd try what Sschick posted. Since it started out fine after servicing and then got worse, it seems like it might be something loosening up.