Dimension by picking entity (the top dimesion) - scales correctly; but dimension by picking endpoints (the bottom dimension) does not scale correctly. Same behavior in old drawing as new drawing. No change to custom dimension style. Tried reverting back to standard dimension style.

Scale factor? Follow sheet dimensions? Tried changing different settings to no avail. 

Some variable must have been reset - I just can't figure it out.

Only change before this issue (as best I can tell) is moving from 2025 SP4 to 2026 SP1. And yes, 2026 SP1 was a clean install (as I always do on the major updates). 

Sometimes I regret updating .....