Moving my answer here as a comment after ruling out this possibility.
Since r2017b, when you change the cd(), the 'current folder history' is updated. When paths from network locations end up on the current folder history and the network becomes unavailable, an undefined variable or function (often caused by a typo) may cause an unbearable delay in the error message to appear.
I dealt with this problem off and on for years before finally coming up with a solution that fixes it. I recently uploaded a GUI to the file exchange that addresses the problem. If this is what you're facing, please give it a try and let me know if it works for you, too.
