Alot of people have been experiencing this issue, and I found a few solutions to this, I only tested one specifically, which is the first that I’m about to tell you.
1st Solution:
1. Right click your model in the explorer window
2. Press Convert To Package
3. Ignore any errors that happens when converting to a package, it may fail or freeze for a second, if that happens it worked.
4. Save the model after converting it to a package regardless of if it fails or not.
The link below is the person who posted this if you don’t understand how I explained it.
The 2nd solution is as easy as Saving To Roblox THEN uploading the model. Might not work, but worth a try.