A freeze, like a complete freeze and needing to restart the game? Or a pause for a brief moment after which the game continues again?
There's a lot of testing/probing involved in determining the power-pole positions, and with the substations even more so because they have a bigger range, so more testing to do. A bit of a hiccup is to be expected.
In case a of a complete freeze and needed to restart, .. well, that shouldn't happen of course.
Either way, would you mind going to the GitHub repository and make in issue there. In that issue, please attach the save file in which you see the bahaviour you describe.
In case you would rather not share your save, I would also be really happy with the pump_planner_input.json
the game saves in the script-output folder.
Keep in mind the file is overwritten every time. So please use P.U.M.P., let the freeze happen, and then make a copy of that json file and attach it to the issue.
With either of those I should be able to replicate the scenario myself and try to make improvements.
Thanks!