I've the same problem. I can confirm that folders expand when opening a new tab under certain (unknown) circumstances. I think that the folders expansion is what makes Textmate2 not responding. It takes some minutes to return responsive, it depends on how many folder levels has to expand. Being not able to find a way to collapse all the folders back with a single command, I'm using another way to create files. Due the fact that neither Finder allows you to create new files, I select the folder in the TM2 project drawer and open a new terminal from TM2 using the shift+Ctrl+O shurtcut and operate from there (also because is easier to add them to git then). Of all the TM2 bugs this is absolutely the most annoying and work breaking.