Whoa! I am assuming that you have a digital readout instrument to measure the peak pressure, and that you are using the same on another cylinder where you have same readout at different different running condition.
First thing I would like to investigate is the instrument: I was accustomed by an old fashioned Chief Engineer to use Digital to quick check, then the usual spring loaded paper ribbon MAIHAK recorder to have a GRAPHICAL readout of the pressure transient. It gives a lot of Hints
It is my direct real experience that on another marine engine the use of reconditioned piston rings caused a lot of problems. If someone fitted one of the compression rings upside down nobody notices until compression is too low.
What about exhaust gas temperature? maybe ten to twenty degrees below the next cylnder?
Do you have original testbench readouts, the one stamped by Classification Society?
I do agree that a misfiring condition is a definitely limited time, limited power takout situation, while I have a very limited experience with 2stroke engines.
If you have a "spillable" oil mist detector sample piping, you may check for abnormal oil mist from the obseved cranck section.
Any way, if you are the Chief, report to the Superintendent and limit the power out: you may be in a dangerous situation.
Let us be informed....