My roof fan has been shutting down randomly with flashing green light and beeping.  (I remove the fuse to get it to stop with the green light.). A while back when this happened there were some bugs stuck in there that stopped it from spinning freely.  Cleaned those out, then it worked fine for a long time. I can't find any obstruction now.  It will run well for a while, then just randomly shut down.  It's happening with increasing frequency.

Anyone else have this problem?  What did you do? Any advice appreciated.