Seems like I fixed the semi auto issue (3:20AM). I swapped the bearing spring guide out with a stock one.
Since I got this gun, I've discovered the following problems.
- Battery is too long (last time I tried to force it and the Deans connector in, one of the wires broke off the battery. There's about 1CM of space. Will probably end up removing a cell.)
- Muzzle had either a paintball or gum in it. The inside of the gun was full of what appeared to be food or other organic material stuck in every possible place.
- Front sight wasn't straight and the handguards were loose.
- Fake bolt gets stuck and the spring isn't strong enough to push it forward.
- Trigger connections were both corroded and covered in grease.
- Vents on piston head were full of grease.
- SCS was installed without removing the nub on the rubber.
- Motor cage is severely loose (not matched to the gearbox)
- 3 missing screws.
- Selector nub worn out (#1 reason it wouldn't fire on semi)
- Current issue (#2 reason it wouldn't fire on semi)
- Nozzle was the wrong type (so it only shot about 10-15 feet).

- 6.03 tightbore poorly chopped to length and has jagged ends. (have not had a chance to test accuracy yet)
- Wiring is worn out in several places (attempts to repair had been done unsuccessfully with both electrical and hockey tape)
- Wiring is nearly broken at several connections and on the battery.
And I don't know how well it has been shimmed - shimming is not something I'm very knowledgeable at.
I bought this from a guy that claims to be a gun doctor... all I knew when I got it was that it didn't fire on semi auto and that he didn't know why.