That I did, every time I would stop the container. Wait till it was fully brought down. Then go mess with the files.
Would edit the file, then double check it was in the right spot, then double check that it still had the edits in it, and then start the container. Once I started the container and went back to look at the file, line 27 in the ProjectZomboid64.json would have reverted from whatever I entered to "-Xmx8g",