That misfeeding issue is a fairly common problem with G&P M4s, and is probably compounded by the fact that the one you bought uses those Uzi magazines. Try loading a magazine, putting it in the gun and tilting the magazine back and forth and see if by tilting it that the feeding problem is resolved. You may need to add some tape or Velcro into the front or back of the magazine well in order to get the magazine to seat properly and feed.
You might also try removing the adapter that allows you to use Uzi magazines and just using a regular M4 magazine.
The clip is junk. However I did plan on removing the adapter. But the adaptor is put on using rivets. They will definitely void the warranty if I remove it. But It doesnt matter. They wont even send me a clip. Well I gave up on them. After a few days of emailing I basically told them Iwill be taking my bussiness elseware. But I do want to get an uzi clip first before I take out the adaptor. Do you know what brands are compatable with G&P? Hopefully a cheap off brand I can get at Dunhams. Because after all I plan on going back to the M4 magazine. Sorry for using the phrase clip instead of magazine. Its habit.