[mcguyver]

I haven't seen this problem in a Marui G36, but I did see it in a G&G UMG (basically the same gearbox arrangement).

The G&G was a brand new gun. When they first came out, G&G acknowledged a defective tappet and offered replacements. The gun I saw failed to feed, so initially I thought that the tappet was broken, as this was a known issue. To my surprise when I opened the mechbox, the tappet was intact. The problem was actually shimming. The sector gear was shimmed so that it basically bypassed the tappet. When the gun was assembled, the sector nub barely grabbed the tappet, like in the thousandths of an inch. After about 40 rounds, it wore the little bit of the tappet away that it did grab, and ended up bypassing it.

I re-shimmed the sector gear so that it engaged the tappet correctly, and altered the other gears to match the sector. To my knowledge, the gun has been running ever since.

Continuous stop/start cylces in semi may allow some lateral play in the sector gear, so that may be why it happens alot in semi vs. full. Usually, once a gear starts spinining it likes to stay in that position, sort of like a gyroscope. This may be why your feeding problems aren't as noticable in full auto.

It's worth a look.