Hello. First time posting here.
Recently I started to get a Runtime error whenever I try to export selection from ROBLOX Studio, which, of course, crashes the program itself.
Here’s the error message I’m talking about:
So far I have reinstalled every version of Visual C++, .Net Framework 4.8, and even ROBLOX Studio just incase. Non of these actions helped me with the problem whatsoever, which is why I’m looking for help. 
This error is likely caused by corrupt components in the Visual C++ Runtime Library. That probably sounds confusing as this is outside the scope of Roblox Studio.
To resolve this issue you could try reinstalling the C++ Redistributable from the download page. You will most like want the 64-bit (x64) version, but the 32-bit (x86) version is available as well.
You may be required to uninstall the existing C++ Package before installing the latest version.
Let me know if this helps and if it doesn’t I can look for further solutions for you.
I reinstalled all of the Visual C++ Redistributables and that didn’t seem to fix the issue.
Update: If you have “Cage Mesh Deformer” feature enabled, then it’s better to disable it at the current moment, as it’s, in fact, the reason why I started to get this error message in the first place…
Hmm, okay. Glad you found a solution. You should report this bug to Roblox if you believe this is what was causing it.