The error says that certain functions that the editor wants to do, do not exist. It specifically says Uncaught TypeError: prevMat.removeMeshInstanceRef is not a function
Here is a screenshot of the error messages.
It seems to be a problem with the imported Render objects. It’s really strange since it worked perfectly about 2 hours ago. I didn’t get rid of any materials or meshes, so I have no idea why I would be getting these errors. The game plays perfectly well, the errors only occur in the editor. I even refreshed the browser a few times to see if that would fix it, but it didn’t unfortunately.
Thank you for your help!
Is it possible to share the project public or add ‘yaustar’ to it and I can take a look?
Which branch, scene and the steps to reproduce would be great. DM if you would like to keep that private
I will DM you regarding access and details.
Subsequently I have tried different browsers to see if it is maybe a browser-specific problem, but the errors persist.
Here is a screenshot of the errors on Safari.
I’ve been added to the project and taking a closer look in a branch.
Looks like it’s specific to the NaturePack_Trees FBX 
Currently looking into this. They will render fine in the game and viewport so please continue working while we look at a resolution to this
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Thank you!
Yeah there’s nothing wrong with launching the game or editing stuff in the viewport, it’s only the thumbnails of the Render files. It’s not really disruptive (except for time as I can’t see what they look like), just very annoying, but I thought I might as well bring it to your attention in case it’s indicative of a larger problem.
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Definitely indicative!
We’ve made a fix and now testing on our staging server
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Thank you! 
Refreshed the editor and I can confirm I no longer get the errors!
