Model #: 33R777
Briggs and Stratton
What year and condition is this mower in? Not sure what to tell you on transaxle issue, except to say get a good flashlight and look around the entire transaxle at the rods, springs, etc. and try to determine anything that looks suspicious.
How do you know it is a broken compression release mechanism on camshaft? Did you check for the “bump” at the valves while slowly turning engine by hand?