I'm attaching a world (whoops, is too big to attach, uhm...) Actually, the datapack is small enough to attach here, so I attached it.

Each time I reload, I get a different number of functions loaded (and indeed, some functions simply are skipped, breaking the game) - from the log:

Loaded 3554 custom command functions
...
Loaded 3563 custom command functions
...
Loaded 3557 custom command functions
...
Loaded 3562 custom command functions

Just do /reload a few times and watch the log.

EXPECTED
all files loaded

ACTUAL
some files skipped (race condition?)