I'm running a ton of little asset mods. I already discovered two of my subways were missing. You can imagine what that did to my traffic.

BrokenAssetException (Affectionately called "Broke-Ass Ex") is just an error that means there's a problem with one of the assets. In this case, it has too many vertices in one of the LODs (Level of Detail)

When you zoom out, the level of detail decreases (textures and geometry are simplified) and there seems to be a hard limit on how big the textures and how complex geometry can be.

Basically the geometry of one of the (presumably custom) assets didn't conform to the new restrictions on LODs.

Were you running any mods or workshop content that contain models?