The exhaust fan stopped coming on the past few weeks on random occurrences. Now it seems to have completely locked up. I tried to open it up to clean the fan and was able to remove every screw all over the purifier except for those in a circular arrangement in front of the fan. There is so much residue around them they are locked into place. The screws themselves are a little soft so stripping was immediate. I tried using a torch to heat up the residue but it didn’t loosen them one bit. Does anyone have experience in fixing this issue or can tech help out. TIA!