I have been using SW for over ten years

Lately I have been having some weird issues with 2d sketching.

I thought it was related to automatic relations but this latest one has me baffled.

first image is before setting dimension - second image is after entering dimension

I have been "working around" these sketching problems I've been having but I would like to get to the bottom of this.

Any insights would be appreciated

I'm using SW2018 SP4.0

EDITED BY MODERATOR: Moved to Sketching space. Please post to the appropriate space when one exists.