Dissolver issue

I'm having an issue with unexpected results in the dissolver

The geometry is validated prior to dissolving but there's a reasonable likelihood of a duff input polygon possibly arc(the shape not the program) related. If i put polygon with count 13 only through an ArcStroker and then dissolve with the rest the output is as expected. But i've not found a way to highlight that this polygon is the problem.

I've attached a template file if anyone wants to take a look, I'm still using 2018 so perhaps this doesn't occur in 2019...