Oh yeah...
upper lower play so excessive the gun wouldn't cycle (parts gun with an EA lower...not to be confused with Eagle Arms)
dust cover spring broke (Eagle Arms - Coal Valley not the later company owned by ArmaLite)
I've owned the followign brands (from memory):
ArmaLite
BCM
Colt
Colt Defense
Core 15
DPMS
EA
Eagle Arms - Coal Valley
Eagle Arms - Div of Armalite
Olympic Arms
Rock River Arms
SGW
Smith & Wesson
Stag Arms
I'm probably forgetting a few.