I just found out how to reproduce this: Edit and save a file visible in Thunar using QtCreator.
Apparently QtCreator (4.2.1) creates a temporary file during saving. When I edit a test.txt file and save it, a new test.txt.YY4824 appears in the directory right before Thunar freezes.
This explains the behavior I have been seeing as I use QtCreator a lot on both machines.
I just found out how to reproduce this: Edit and save a file visible in Thunar using QtCreator.
Apparently QtCreator (4.2.1) creates a temporary file during saving. When I edit a test.txt file and save it, a new test.txt.YY4824 appears in the directory right before Thunar freezes.
This explains the behavior I have been seeing as I use QtCreator a lot on both machines.