There are several possible causes and more info would be needed to properly diagnose the cause. However, production 1911's are assembled with drop-in parts, rather than fitted parts. That goes for the barrels and bushings and a fit that is jsut a bit too tight can cause malfunctions as the barrel heats up it expands and creates greater friction. This was a common problem encountered back in the early days of IPSC, etc when people took tightly fitted bullseye pistols (where you typically fire five rounds then put the gun down) and put them into rapid fire, run-and-gun type of shooting, they just locked up when they got hot. Another cause can be shooter induced, due to shoter fatigue and fialure to keep the wrist locked after a nomber of rounds have been fired.
1911's need very little lube to run properly, a little bit of a good lube like Slip 2000 EWL is all thats needed.