inscrutible, that's what you are

I really want this answered by someone who works for SolidWorks.

My sketch contains an entity with unsuitable geometry.

There.  That's all the information you get because that's all the information that alert gives me.  Fix my problem.  Start by canning the person who thinks that "The sketch contains an entity with unsuitable gioemetry" is useful.

SolidworksParts And Features