Strums and some notes not getting registered or getting good or early in score attack.

so iv always had this issue of whenever there is strumming i will always get a random mix of perfect or good or early (score attack) or sometimes straight miss no matter how perfect i strum. also happens with notes. dosent matter if its a lot of notes or singular very slow ones. its random. i usually didnt care about this but since iv started participating in rocksmith championship week id like to get this fixed as its very discouraging to see my accuracy and score being bad even though im playing as best as i can. i have tried everything from changing my buffer size from 64 to all the way till 256 (any above that and the latency gets bad) to changing the latency buffer from 1 to 4. manually inc the gain override. changing my guitar action changing picks. nothing worked. btw im using nux mg300 as a audio interface through reaper with the asio mod. tried it without reaper too and still nothing. also have some problems with muted notes. so sometimes they will get registerd and sometimes they wont but if i play the muted notes without muting them they get registered consistently. im guessing its a gain issue? but iv tried inc the gain and it still happens randomly. iv heard about using thicker strings currently using 9-42 is that the problem? any help is really appreciated!