Had a bunch of biters spawn in my base and wreak havoc. I guess they ended up killing a lab with production modules in it and got this assertion fail:

2906.767 Error MainLoop.cpp:1435: Exception at tick 7054341: The mod Newly constructed machines wait for their modules (1.1.17) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event newly-constructed-machines-wait-for-their-modules::on_tick (ID 0)
...onstructed-machines-wait-for-their-modules__/control.lua:147: assertion failed!
stack traceback:
[C]: in function 'assert'
...onstructed-machines-wait-for-their-modules__/control.lua:147: in function <...onstructed-machines-wait-for-their-modules__/control.lua:131>

I have a lot of mods installed so not sure what might be causing this problem but if I had to take a wild guess I'd say it could be https://mods.factorio.com/mod/Repair_Turret that rebuilt the lab.

if you're able to reproduce this from your latest autosave please ket me know

It does seem to happen within about a minute in this autosave: https://drive.google.com/file/d/1QNAbNjLlceCAATLoiNZxcR49ZaIYQWgo/view?usp=sharing

Note that I have a few mods manually edited to make them compatible.
Here are just the modified mods, ~300M (rest should be downloaded when syncing with save): https://drive.google.com/file/d/1dFTc3yhvJw2CRQeblAtdaL50J_8Sz1_V/view?usp=sharing
Here is the whole mod dir at around 3GB in case you want to get it all in one instead of syncing in-game: https://drive.google.com/file/d/1MfXNUtiQaULLQUS9fA6AEi9lKyvWIsIC/view?usp=sharing

allright so just loading the save and doing nothing for about a minute reliabily triggers this? nice

Yes, at least for me for the few times I tried.

excellent thank you, it happening several times is good news, I'll try to download and test this later today

thanks for your patience and your autosave with excellent reproduction steps, 1.1.18 should no longer crash, hopefully the fix has no unexpected effects.