@jwr.rom, thanks for the instance.
I feel I see what the issue is. In my instance above I had solely edges for SketchUp to cope with, not 100% like what you’re employed with.
In your instance SketchUp wants to mix ‘“tangent” with one edge and one final section of an arc.
Cut up of the final section of your arc by drawing a short lived edge from the final however one endpoint.
Then explode that separate final endpoint (which continues to be an arc). now you have got two edges operating to a mutual endpoint and the operation in poor health work on sharp edges.
Then delete that quickly drawn edge.
