Thanks for your answer, Jonathan.
Looking at the three reasons why code gets frozen, 2 and 3 are easy to deal with, since it is my own code. It remains 1:
" 1. The code that's running doesn't have source references, so the debugger doesn't know what file it came from."
. You provided a link to the paper Source References by Duncan Murdoch. It is a bit old, as it has been published in 2010 and parts of it are well over my head. Is there a simple way to add source references to my code so that I can debug "live"?
Thanks for your help.