Consider this a report - I doubt you can easily fix it, and I'm not asking you to.

Cliffs which were destroyed, on worlds where this mod's functionality was post-implemented, are respawned.

In one case, confusingly, a core miner was destroyed and replaced by a sealed core seam. On that world, another core seam is sealed, but it didn't have a miner on it. Most seams are unaffected. No other core miners are missing. This world does have a lot of cliffs. I'm not sure what to make of this behavior TBH. Hence I'm just reporting it to you in case it means anything to you in terms of any workarounds you may have done.

Some more info - it definitely respawned respawned some cliffs under an array of accumulators. Didn't notice until I was tearing it down

Fixed the cliffs. Hopefully, it won't affect the core seams anymore either; I really don't know exactly what would be going on there. (Are you able to test that?)

Not really, I've updated all of my surfaces. Well, I can load an old save actually.... But I have to update mods as well... And that means backups of the mods because I'm not getting bitten again by that. I'll test it later and report back.

I do have half a theory though. Not that the bots care about having cliffs in the buildings that I've seen, but if they did decide to, then near misses on the core seam does seal it - I've seen that in the last week

Bad news mate. I watched it happen in real time.

Quick question first - are the new resources seed based or is there anything that could make them different on this update? My computer is too slow to load and unload mods and massive saves and wait for factorio to check consistency to answer my question, but I don't remember there being an ore deposit right below the core mining drill last time.

Anyway,

1) The core mining drill which was missing last time is now sitting on tantalite ore, and claiming "no minable resources"

2) The other core seam is sealed again. It is not directly adjacent to a still-existing cliff. BUT, it does have indite ore pasted partly over it.

I think that what's happening is like when you super force build a building over a core seam...

Funny coincidence it only happened on one planet, and right near each other.

There's a seed involved, yes. So it should be the same every time.

I think I'm going to have to spend some more time looking into how core seams actually work. Even if it's rare, I don't want to break things at all. Certain of the things you've said are giving me a theory, at least...

It looks like sometimes when resources are copied into a region occupied by a core seam, even though it doesn't overwrite the seam itself, will either seal it (and destroy any core mining drill present) or cause a drill present to jam; I'm not really sure what results in one or the other happening. I've added some code that tries to prevent that from happening, but it only mostly works; I've got a theory on that but I've run out of patience for messing with it tonight.

Anyway, the new version should have issues much less often, and if you have a drill that's jammed, removing and replacing it should fix it.

Yeah, I lost a drill in the update - I don't much care about it. I've got a world missing decoratives too. Not bothered.

The fact you put in the time to make this mod and in particular make it usable on worlds already in play means a lot to me. It means I'm playing through to the end now, unless something very buggy comes up when I stop blueprinting and get back to science advancement. Not so sure I could have otherwise. At least it would have sucked.