I wanted to add a few mods to my save, however the game crashes when trying to save. I believe it is something to do with the error "Error FluidBoxManager.cpp:517: fluidBox->isInFluidManager() was not true" However, why would that bug out just by adding a mod. I tested with multiple mods, and even updating/downgrading mods as well as updating this mod, and it always bugged out in the same way. An earlier save of the world IS able to be saved with any changes, and does not crash. A similar issue was found here:
https://forums.factorio.com/viewtopic.php?f=7&t=77971

Here is my log file.
https://tinyurl.com/vbz3sed

That's terrible to hear and I'm sorry about your save. Unfortunately I don't have any clue about why this might be happening. It is true that my mod performs some logic specifically when the "configuration changes" (i.e. when mods are added/removed/updated or the game is updated). However, I can't seem to reproduce the issue (even in the saves with a similar issue on the forum). This leads me to think it might be an issue in combination with another specific mod or perhaps in the base game. Also the error happens on the C++ side where I only provide lua scripts..
Unless anyone has any suggestions on how this could be fixed, there's very little I can do. Let's hope the devs find a solution soon!
My sincerest apologies for the inconvenience,
Joey

I think I found the culprit, one air filter machine 2 did not have a pollution slot, and if I tried to destroy it the game crashed in the same way as before. So I loaded back my save after reverting all mod changes and broke those machines, and saved. Then I did the update and added the mods and there was no crash. After a second look the machine that crashed me also happened to have a full 50 used filters in their output. So that worked as a quick fix. Migration wise that might be a bit harder to track down.

ah this resembles my issue and i'm using super deep stack sizes with BigBags mod so it took an eternity for my used filter count to reach its maximum in the furnace, maybe this is the problem. . or at least a part of it. for now, i have to let the pollution rip in my base and not manage any of it.

Duplicate: https://mods.factorio.com/mod/better-air-filtering/discussion/5e0ce6a2f6c44b000de49b2c