It’s likely an add-in conflict. The Rhythm error is ignorable though as it is not a “real” error. Rhythm is made by targeting a lower RevitAPI dll and Dynamo gets mad and throws that ridiculous error for it.
But your addins could be loading DLLs that are causing Dynamo issues. (XceedWPF is a big one).
@jacob.small normally has a lot of good info about this (like the post below):