User347430248 posted
Hi kszymaniak,
Are you developing any .net core project?
If No, then you can try to repair your Visual Studio 2013 from Control Panel and again check whether this issue get solved or not.
It is possible that some Visual Studio 2015 component remain when you move back to VS 2013.
From your description, It is not clear that how did you move back to VS 2013.
Did you first completely remove the VS 2015? then install VS 2013
If not, You can try like this to avoid any issue in VS 2013 version.
Let us know about your testing result.
We will try to provide you further suggestions , If needed.
Regards
Deepak