We've released UModeler 2.8.9f2 for hotfixes.
A few issues in the Hotspot Layout Editor were found so we had to fix them as soon as we could.
Here is the changelog of 2.8.9f2.
Asset : Includes the Basilica Cathedral Package for 2.8.9 users.
Fix : Fixed constant GUI errors which were thrown while in the Hotspot Layout Editor in Unity 2021.2
Fix : Fixed a bug where Hotspot Scriptable object doesn't get saved and is reset after each Unity Editor in Unity 2021.2