I will try to debug it if I can reproduce it. Trying "self halt" in a
workspace followed by a proceed in the debugger did not make my image slow.
So, how to reproduce that bug?
Try and create *lots* of large overlapping windows, including a transcript. Then write some code that writes something to the transcript and put a halt in it. Then proceed. That seems close to what I'm doing. HTH and thanks for taking a look!