KJW M4 not cycling properly?
 

Recently got another KJW M4 (I love these damn things, what can I say? :) )

Anyways it doesn't seem to cycle properly... what I mean by that is.

I can fire semi auto with absolutely no issues, I kick it into full auto and every 3rd or 4th shot the bolt will lock as if there's no BB's left (but there is!!)

I had a similar issue with my other KJW M4 and I just swapped the rear pin (it was loose) to a bolt and now it fires like a dream, but this isn't the case with this M4

II've found a temp solution (and its a weird one) but putting gorilla tape on ALL the pins.
this to me says something is moving ever so slightly but I have NO idea as all the pins are rather tight.. any ideas?