I've seen the same issue with the original 81 tiles mod. Cities:Skylines have obviously changed something that these extra tiles mods reference.

I confirm it happened to me too. I personally got this message :(

"Array index is out of range. [System.IndexOutOfRangeException]"

I started a city with the mod on, then saved it, next time I wanted to play, I get this error. When I disabled the mod, I still get the error, and now I cannot access that city because I get a popup with that error message forever... :(

The original 81 tiles mod hasn't worked since the 1.15 game update (which is why this one was developed as a functional replacement).

Your log shows multiple broken mods throwing errors: Compass mod, Trees Respiration, etc. Also Real Time is showing isses, too (known: it needs updating).

Unusb (not just disable) those mods and see if the issue persists. If it does, post an updated log without those mods and I'll take a look (at the moment there's too much error spam from those mods for me to be able to pick out anything else).

I've seen the same bug in my game:
Division by zero [System.DivideByZeroException]

Same answer.

Hi algernon.
Thank you for your answer and for your work.
After a careful check, I could say that:
1. The "division by zero" error was related to some districts which were broken. I had to cancel them from one corner of the map where they were "moved" and after redrawing everything was fine.
2. The problem was not on the mods you mentioned, since it was still present after unsubscribing them. Anyway, the problem disappeared by itself just after few days. Maybe it was some other mod conflicting which has been then updated and fixed.
Thus, I think I can not help understand which was the source of the error.

That does indeed sound like old corrupted district data. Note that incompatible mods can still cause that if the save was saved when they were still active, even if they're later unsubscribed.