Union Function stops working

[dburtis2]

Visio Pro 2401 version (Build 17231.20194 Click-to-Run). Local Copy on Windows 11.  Using Union function to combine many shapes to follow some curves on drawing. After about 30 - 50 successful unions of small shapes with color and no line, union function stops working correctly (no change in type of shape). I either get a err #-1 or the shapes I'm trying to combine disappear.

Got any ideas why this is happening? I've used Visio since before is was bought by Microsoft.

[Yacine]

too vague