Slowdown while debugging - Is there a proper way to exit a running session?

[RoryWatts]

I feel silly even asking this question...

I have been using nvim-dap for debugging python successfully for the past few weeks.
Recently, I have noticed a great deal of slowdown when stepping to the next (F11) item, or running commands in the REPL.

My operations are fairly trivial in terms of actual runtime. Running the entire script takes about half a second, but waiting for nvim-dap (e.g. querying a high-dimensional numpy object) to run one step in this script often takes 30-40 seconds. This seems to be getting longer.

I wondered, am I doing something inappropriate when running nvim-dap? To start a session, I type F5 and run the script. To close the session, I mash F5 a bunch of times until I'm prompted to close the session , and then I re-run it again pressing F5.

I thought nvim-dap may be slowing down because I'm not closing it properly, and there is some memory leak in the background perhaps? If not, is it common to experience quite slow debug times in python with numpy? I'm using neovim, and have nvim-dap-ui installed, but don't often use it, as the repl does most of what I need.

Thanks in advance