Originally Posted by Ablebaker
Speaking of the thumb safety. The hammer flops back and forth regardless of whether the mainspring housing is in place or not.
If the hammer strut is in the Main Spring Housing correctly, there would be too much pressure for the hammer to "flop" except if something is broke.
I do not know your experience level with disassembling or reassembling a 1911, but I would suggest that you get the firearm checked out.
It could be that when you are reassembling, that you could be missing a step and not know it.
To me, it would be worth $25 for a quick lesson.