When creating a new scoreboard objective, it's possible for 'dummy' to neither show up in the criteria options or function as a valid scoreboard criterion. This bug does not affect objectives made prior to loading up the world, as they will stay in the world's data/scoreboard.dat file with 'dummy' still set as their criteria. This does affect datapacks greatly, as whenever the issue arises (which is occasional), datapacks are unable to recognise any functions with a /scoreboard objectives add <name> dummy command in them.

Unchanged log file is attached as requested. I only noticed the issue about 30min into play.