Issue is as said in the title, all I did to replicate it was "try to place a pair of Express (blue) underground heat pipes by construction robot on Aquillo next to a roboport that was frozen", and the same thing happens with a very small difference in the error message when I do it manually with items in my character's inventory. It happens as soon as the FIRST one is placed. Underground heat pipes that were already placed are not throwing errors, and seem to be operating as expected.
This has put my construction of my Aquillo base on hold until this is resolved, and I was really looking forward to getting that Fusion power stuff working.

here's what I have for the crash window itself:
-/
The mod Underground heat pipe (2.0.7) caused a non-recoverable error.
Please report this to the mod author.

Error while running event underground-heat-pipe::on_robot_built_entity (ID 15)
underground-heat-pipe/control.lua:58: attempt to index local 'old_entity' (a nil value)
stack traceback:
underground-heat-pipe/control.lua:58: in function 'bring_heatpipe_to_front'
underground-heat-pipe/control.lua:279: in function 'check_for_neighbors'
underground-heat-pipe/control.lua:289: in function 'update_mode_for_all_pipe_to_grounds'
underground-heat-pipe/control.lua:227: in function <underground-heat-pipe/control.lua:194>
/-
Here's the log file from a cleared out log and only replicating the bug:
https://pastebin.com/vk1AS13a
Pretty much only shows the mods I have installed and the stuff I typed out above from reading the crash window, for what it's worth.

a video and a save file would be appreciated

No software for a video, unfortunately. As far as the save file, I'd need a place to host that.
However, I do have additional info: Any attempt to REMOVE/pick up an underground heat pipe that's been placed will ALSO result in a fatal error, and yes it's got the same stack trace to it.
What I haven't done is check to see if a brand new save file will have this issue or not, if it does that would reduce the save file size I need to upload by a lot.

EDIT: Seems like it might be an issue with that save specifically, not sure how that could have happened but I think I can recover the save without deleting the whole thing, I just have to delete Aquillo and regenerate it.

Thankfully fixing the issue seems to not have been that difficult after all, disabled the mod, reloaded the save, let that purge all the underground heat pipe stuff out of the save file, saved the game, then re-enabled the mod and reloaded the save again and all seems to be well.
Sure was a strange issue tho.