I don't know how I produced the bug, and alas have no repo case but happened twice. In Unity version 2019.3, PM 1.9.0
When trying to type a name into the state naming text box, the field is unselected after every key stroke. So you have to click on it for every single letter.
Fortunately, there is an easy fix: resetting the layout in the upper right corner fixes the problem.
I have not tested whether other text boxes in PM are affected as well, but it did not affect Unity windows.