As stated, the server corrupts the ops.json file when the server starts and when the /op command is used in the console.

If the server starts with a populated ops.json file from a previous version, the file is corrupted, leaving only an open bracket in the file (see attached file).  If the file is missing or has no players in it, the file is formatted properly ("[]").

This corruption also occurs when trying to op a player through the console.  The console takes a second before returning "An unexpected error occurred trying to execute that command", then the ops.json file is again left with just an open bracket.  If you op a player through the console, get the error, then op them again, it says they are already an operator, suggesting that the server is keeping server ops in memory, but cannot save them to the file.

At the moment, the ops.json file must be manually edited after startup to add players properly.

This issue does not appear to affect previous versions before 20w09a.

Attached is an ops.json file that was created by an affected server at startup, 2 players were opped through the console, then the server was stopped.