Don’t know where to turn. Having a problem with GTN 750 in Milviz Otter in Prepare3Dv4.1. At beginning of flight it works normal. Cockpit mount works and when I choose drop down or stack gtn 750 the cockpit gtn 750 screen goes black as it should. After about a half hour if I use the drop down both screens stay lit with the drop down map frozen but when I use the keys in the drop down it effects the cockpit mounted gtn. The cockpit mount continues to work but I can no longer use the drop downs. I tried changing the cpu core # to 1 but problem persists. This is the only Milviz aircraft I own. Any suggestions appreciated, Thanks.