Assertion failed on expression: '(int)lastVertex < GetVertexCount()'

Upgraded from Unity 2017.4.8f1 to 2017.4.9f1 and got this exception:

Assertion failed on expression: ‘(int)lastVertex < GetVertexCount()’

Seems to be related to combining static meshes. A few of the meshes that are marked as static gets vertices all over the place.

Anyone else getting this?

Aby luck finding the cause or fix for this @huhund? We have the same error related to static batching in 2020.1,Any luck finding the cause of this or fix? We have the same error also related to static batching.