This happens when I try to use OOP on a sulfuric acid source on Vulcanus:

The mod Oil Outpost Planner (1.6.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event OilOutpostPlanner::on_player_selected_area (ID 53)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__OilOutpostPlanner/layout.lua:142: in function 'AddLandfillUnder'
OilOutpostPlanner/layout.lua:1589: in function 'Plan'
OilOutpostPlanner/control.lua:50: in function <OilOutpostPlanner/control.lua:37>

Interesting. I can't easily reproduce this issue.

I've pushed a new version (1.6.2) which might avoid the crash, but doesn't fix the underlying bug.

Are you able to provide a save game that can reproduce the issue?

Yes, of course, but how do I attach the save?

Yes, of course, but how do I attach the save here?

I don't think there's a way to attach a save here. Usually folks put them on Google Drive, or some similar site.

I don't think there's a way to attach a save here. Usually folks put them on Google Drive, or some similar site.
I figured it out :)
https://drive.google.com/file/d/1GH7MpxxOOU1J2MCMW7pdHk61z0VJnWRy/view?usp=sharing

Thanks. I got the save. I assume the sulphuric acid patch giving you trouble is the one right next to the engineer when loading the save. It doesn't crash for me, but that's probably because the Planner settings you were using with OilOutpostPlanner got reset to defaults when I loaded. Can you tell me what settings you were using? In particular, what power pole type, beacon type and min beacon utility? And was anything at above-normal quality?

Never mind, I get the crash when I switched to substations, so I should be good to debug it now. Thanks!

I used the standard settings. Just swapped it out for big electric poles.

When I select OOP to an area without rocks - the error sometimes doesn't occur

OK, I've released 1.6.4 which I believe should fix this issue. Let me know if you run into any other problems.

Do you really mean big electric poles (not substations)? I wouldn't recommend using big electric poles; there's a decent chance OOP won't be able to find a valid pole layout (especially on Vulcanus) because a pumpjack is completely surrounded by pipes and other pumpjacks, so there's nowhere for the pole to fit. You'll have better luck with medium poles or substations (or even small poles!).

Thanks you so much :)
Yep, I used to use big electric poles (like on Nauvis) out of habit. Thanks for the advice, I'll use medium poles or substations