Gain issues on M32R

New

Hello, 


maybe I missed a thread about this but, we have been using a Midas m32r at our small church for several years. We have had a pro tech come in and help us reset the board and set it back up. We did that because we were having issues with the volume dropping out mid service. We are still having this issue. I have narrowed it down to the gain control on the channels not working properly. When turning up the gain it doesn't change anything until it hits about 75% then it "catches up" and won't turn back down. Then after a while it will drop out and get quiet again. Any suggestions?