I think it is the trigger, at least on mine. Many think the trigger is great but there is something there that I find to be slightly disconcerting. I can't place just what it is but it is there, kind of like a subliminal message. That said, I shoot the 52 quite well when taking deliberate aim with it, even better than most 1911s I've owned. Its just there is something about it I find potentially distracting and that shows up when firing more rapidly for me.
The 2 main differences I found when I shot them are
the M52 has a pivoting trigger not a sliding one and the barrel slides back not a swing link
so the 1911 seems to cycle faster,..I swear I can feel the slide moving when the 52 cycles
I think the difficulty I had was the timing of the shots and wanting to rush them feeling like I had to make up time for the perceived slower slide cycle and sacrificed some follow through and trigger control which opened up the groups
I think its a trigger time thing, sort of like the readjust from a S&W M41 to a Browning Medalist grip angle