Please make sure to report bugs on our support forum and include as much information as you can about what's happening, how to trigger it, and ideally also the output_log.txt (called player.log on Mac and Linux) and the save where this is happening. Thanks!
https://forum.paradoxplaza.com/forum/forums/support-bug-reports.879/
Depending on your operating system the log can be found here:
https://forum.paradoxplaza.com/forum/forums/support-bug-reports.879/
Depending on your operating system the log can be found here:
Windows
\SteamApps\common\Cities_Skylines\Cities_Data\output_log.txt
\CitiesSkylines\Cities_Data\output_log.txt
Mac OS X
~/Library/Logs/Unity/Player.log
Linux
~/.config/unity3d/Colossal Order/Cities: Skylines/Player.log