After working just fine for about 1,200 rounds, my gun is struggling to cycle unless I oil it excessively

Build:

14.5" BCM MK2 EMW mid length BCM BCG BCM mod 1 T1 buffer BCM spring (Have also tried mod 1 T0 buffer and green springco spring in different combinations, same issues)

Ammo:

55 grain FMJ 62 grain FMJ

Both of these have worked in the gun just fine before but struggled yesterday with different combinations of buffers and springs mentioned

I clean and oil my gun after every range session

Any ideas as to why it's suddenly not cycling? The trigger was not resetting on majority of non-cycles as well