In the latest FC0.18, every time I edit a (blue) reference constraint in the sketcher, after leaving the dialogue window it turns into a (red) driving constraint.
I suppose this is a bug?
Consequences are, that if you have a fully constrained sketch and eventually want to name some of the reference constraints, you can't do it. After editing, the constraint still has no label and I get the message
"Dimensional constraint - Negative datum values are not valid for the constraint with index $some-number"
and then, since the sketch is now overconstrained:
"Not allowed to edit the datum because the sketch contains conflicting constraints"
OS: Ubuntu 18.04.1 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.15697 (Git)
Build type: Release
Python version: 2.7.15rc1
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)
: added ticket issue #3793
to thread title