A friend of mine that does not use GSE or TSM has this issue regularly, thus I can say it is definitely not GSE or any macros. He does use Healbot as a holy priest and that will also freeze up on him at times. Still no fix on his side. Could be a random bug in blizz UI which I get sometimes in my !Buggrabber addon eg: error when going into an instance but does not lock anything up as I use ElvUI as my UI and not Blizz default UI.
I think, therefor you are !