Don't want to get anyone's hopes up yet until I have tested it further, but I did manage to disable full marks in the current event.
I was on a test account which I hadn't used in a while, so it wasn't up to date. This meant that file editing wasn't possible yet as the game would have redownloaded the new files, but memory editing was possible.
I turned on airplane mode after launching the game to prevent my save from syncing, and then I used cheat engine to try string editing "Y1_C6_P1" to something of the same length, however the game would crash as the thing that I edited it to didn't exist (to stop the FM from triggering). This meant that what I replaced the FM starting criteria with needed to exist in the game files already.
I settled on replacing "isGoalComplete(\"Y1_C6_P1\")" with "not(skillUnlocked(\"duro\"))" as these are both the same length. I then turned off airplane mode and noticed that the game was now working properly, and that no FM was in my events.
To make sure this wasn't just the FM being invisible on my game but still being sorted on JCs server, I will log back on after it has ended and see if it is in my event log or not.