If it automatically starts going into full auto it is a noid or board issue. My FX used to have that problem, and I fixed but I forgot how. Sorry. But, honestly, the FX doesn't have much resale value at all. I tried selling mine for 150 with a parts kit but everybody tried to get me to drop it to 50 bucks. I personally would keep it as a back up gun or just hang it on your wall, unless you desperately need $50.
I just got a luxe oled and also have a etek 4 so i dont think i really need a backup to my backup. I wasnt going to try to sell it on forums anyway i was just gunna see if any of my friends wanted it lol I'll probs call DP and see if its worth fixing