I own an M1A and have experienced feedback issues at open mic nights in 2 different acoustic guitars. I keep the volume on the pickup wide open. Would turning the volume down on the pickup help? Otherwise, the warranty has run out and I am just going to trash the pickup or give it away. What a waste of money!
You should be able to keep the volume on the pickup at full. I wonder if there may have been conditions in the open mic venue and sound system that could have contributed to the chance of feedback.
Before assuming the pickup is just bad, would you like to send it in for testing? I'm flexible with warranty cut-off and can extend coverage under certain circumstances.
If so, please contact me at [email protected]