Why is my Fisher Paykel dryer making a growling sound? ?

This is my second FP dryer. The other one started going bad with the same sound. The repairman said it was a bearing on the first dryer, but replacing that didn't fix the problem for long. When this dryer was new, it ran quietly. It took only a few months for it to start growling when the drum is turning in one direction. It doesn't growl when the drum reverses. I found this video on youtube, and it sounds like my FP dryer. http://www.youtube.com/watch?v=71TH5LTVGfI