Property Types Editor form not saving to disk newly added properties #3374

My OS is Ubuntu 20.04.2 LTS. I'm using v1.8.5 from the snap package at snapcraft.io with full permissions granted. The enums and classes added to the menu "View" -> "Property Types Editor" (while a tsx file is open and selected) do not get saved after the app is closed. After restarting Tiled, the previously added properties do not get restored. The "Import" and "Export" buttons works as expected. Object types (from "Object Types Editor" form) do get restored after each restart, but object properties of type "property type" (enums and classes from "Property Types Editor") are casted to other types due to the missing property types.

Steps to reproduce the error:

1. Open Tiled.
2. Open tsx file and select a tsx file tab.
3. Open "View" -> "Property Types Editor".
4. Add an enum and a class.
5. Click on "File" -> "Save"
6. Click on "File" -> "Save all"
7. Close Tiled
8. Reopen Tiled
9. At the tab from the same tsx file, click on "View" -> "Property Types Editor". Last changes are missing.