Datapack dimensions vanish after reopening world

[arconyx]

When a custom dimension is added through a datapack (with an appropriate custom world preset) the dimension is accessible (via execute in) in newly generated worlds but not after the world is closed and reopened.

Notes

• I have confirmed that this does not occur with only Minecraft 1.19.3 (and Quilt Loader v0.17.8).
• Once QFAPI/QSL (QFAPI 5.0.0-alpha.5 and QSL 4.0.0-beta.2 for Minecraft 1.19.3) are enabled the problem appears in both new and existing worlds. Specifically, custom dimensions are inaccessible unless the world has just been generated. Affected worlds continue to have this issue after disabling QSL again.
• In an attempt to rule out QFAPI, I extracted the various individual jars from the QFAPI/QSL jar. After using only the mods without fabric in the name I found the problem still occurred. Disabling the Quilt Dimension API stops the problem from occurring.
• /reload appears to work without issue. It does not cause dimensions to disappear or to reappear.
• Inspecting level.dat shows that the custom dimension is listed in WorldGenSettings > dimensions after the world is generated. After the world is reopened the entry for the custom dimension disappears.
• Likewise, the log files show chunks from the custom dimension being saved on during the first session. Once the world has been reopened this is no longer the case.
• I've also observed this problem on 1.19.2. A server running said version has had no problems since removing QSL and dependant mods, despite continuing to run other mods (Lithium, etc).
• The dimension data is not removed from the world files. Removing level.dat and the overworld, then loading the world again without QSL allows access to the missing dimension. This was tested on a server, where the world type could be specified in the config files. In singleplayer this did not work, presumably because it was regenerating the world using the default Minecraft world type (which lacks the custom dimension).
• Exiting the save while in the custom dimension causes the game to kick you back to the overworld on next load.

Reproduction

I have attached a datapack minimal-dimension.zip to demonstrate the issue.

1. Begin creating a new world. Enable commands and the attached datapack.
2. Select the generator.arc.beyond_preset world type.
3. Create the world
4. Start typing the command /execute in. Autocomplete will show arc:beyond as an option alongside the vanilla dimensions.
5. Save and exit to the title screen.
6. Reopen the world.
7. Start typing the command /execute in. Autocomplete will only show the vanilla dimensions. Attempting to run a command in arc:beyond anyway displays an unknown dimension error.

The attached log file dimension-issue.log is of me following these steps, although I did not go beyond autocomplete in step seven.