Perhaps your approach to the back 9 needs a new "offensive coordinator". I'm betting that consciously or unconsciously you're playing a bit defensively to start the back 9 to preserve your score... and get into the 70's.
Go after it on the back side, try to beat your front 9 score. What have you got to lose?
Shot 85 (43/42) Sunday, 11 nGIR/GIR, 30 putts, 2 penalty strokes (both on approach shots).
Started with double bogey on #1 then hot mess of a quadruple bogey on #2, which set the round off poorly, but played okay after that with a couple hiccups along the way.
Full swing is still the biggest obstacle to consistently better scores. Thinned a couple pitches that were costly, but also had three almost chip-ins, so I would say short game was good enough. Still gaining strokes putting.
Strokes gained vs. 5 hcp:
Tee = -0.92
Approach = -6.01
Short game = -1.07
Putting = +0.44
Well, shooting 83 at a 12.7 is a decent round no matter how you did it. With each time you near par, you are showing yourself that you do have the ability to play good golf. My question to you is how did you feel at the turn? A 57 is a serious meltdown.