I encountered a reproducible crash (save available to reproduce if needed).
The error:

Error while running event biter_reincarnation::on_tick (ID 0)
biter_reincarnation/utility/functions/biome-trees.lua:39: attempt to call field 'tileTempCalcFunc' (a nil value)
stack traceback:
biter_reincarnation/utility/functions/biome-trees.lua:39: in function 'GetBiomeTreeName'
biter_reincarnation/utility/functions/biome-trees.lua:74: in function 'AddBiomeTreeNearPosition'
biter_reincarnation/scripts/reincarnation.lua:112: in function '?'
biter_reincarnation/utility/event-scheduler.lua:91: in function 'handlerFunction'
biter_reincarnation/utility/events.lua:94: in function <biter_reincarnation/utility/events.lua:89>

Rolling back to 20.0.14 seems to fix the issue; maybe an issue in the migration code?

I had to rewrite large sections of logic to support alien biomes in the latest update. I have a horrible feeling I didn't regression test the mod, as it turned in to a real pain to get AB working and I'd had enough.

I will have a look and hopefully it's a simple patch/migration script to resolve the misalignment.

if you do have a save that would be good. As it doesn't happen on me loading my existing 20.0.14 save.
I don't see how its reaching that code as it does look to be mod version change safe, or atleast not crash.

If the issue still occurs with new release 20.0.16 please post the save game.
I have made changes to make the code around this safer just based on the error stacktrace.

I've updated, and reloaded the crashing save, and it's all fine, thanks!
Just in case, you can find the save at https://files.xelnor.net/biter-reincarnation-crash.zip

And thanks a lot for the very quick bugfix, it's really appreciated!

Oh, I see what's happened; I've done something naughty in Factorio modding and for some reason you ran in to it as an error.
My latest fix resolved the symptom you had as part of fixing a wider legacy lazyness of modded tree/tile approach. But on looking at your save I see my fundamental mistake. This will still cause issues in the future so I will release another fixed version now that does it the approved Factorio way.