Error is:

The mod P.U.M.P. (2.1.8) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event pump::on_player_selected_area (ID 53)
LuaGuiElement API call when LuaGuiElement was invalid.
stack traceback:
    [C]: in function '__index'
    __pump__/toolbox.lua:585: in function 'pick_tools'
    __pump__/toolbox.lua:701: in function 'add_toolbox'
    __pump__/control.lua:96: in function 'process_selected_area_with_this_mod'
    __pump__/control.lua:10: in function <__pump__/control.lua:8>

Hi, thanks for the report.

I thought maybe it's the latest update. But I just updated and it doesn't happen for me. So, that's going to make it hard for me to fix. 😅
Is it something you encounter repeatedly? And if so, can you provide a save file in which it happens?

The error suggests something in the UI, though. So it might just as well be the order you've clicked things, rather then the state of your playthrough, or the resource patch you're planning. If you can provided a step-by-step guide of how to reproduce the error, I'll happily look into it. 😊

Strange! Even stranger it was happening repeatedly but appears to no longer be doing it.. I haven't changed a thing either. Sorry for the bad report!

No worries, an error happening isn't a bad report. Some errors are just harder to explain or reproduce then others. It's still good to know an errors hides in here somewhere. Something to keep my eyes peeled for.

Feel free to come back to me about it if it happens again.