Description of the bug:

I have 5 identical advancements with 5 advancement rewards-functions that print which advancement was received. All advancements are triggered when I hit the zombie. The advancement order is seemingly shuffled upon every /reload.

You can find the data pack I used for this attached below if you'd like to replicate it yourself. 

Steps to reproduce:

1. Install data pack in worldsave's datapacks folder.
2. Type /reload
3. Hit any mob
4. Type /reload
5. Hit any mob
6. Look for the order in chat

Expected result:

I would expect them to execute either in the lexicographical order of their filenames (i.e. 1.json and it's function first, 2.json and it's function second) or order of their 'date last modified'. For this example, I made sure those are the same. Even the rewards-functions are ordered alphabetically by name and by 'date last modified'.

Actual result:

For all intents and purposes random.