Edited to reflect the following tickets:
issue #3791 (Solver fails to find redundancy, in orange)
issue #4032 (Solver falsely claims Sketch to be fully constrained, in green)
Note: for Advanced Solver Control I was using DogLeg Solver for both the default Solver and Advanced Solver
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I'm wondering how the Sketch was created, because when I open the file the Status Bar message reads:
Touched (but must be executed), Internal name: Sketch"
I can apply the 8 mm Horizontal Distance Constraint to the horizontal line segment and the Sketch mistakenly becomes Fully Constrained.
Even after doing that,
I can apply a Tangency Constraint between the arc and either vertical line segment and the Sketch mistakenly becomes Fully Constrained.
After applying a similar Tangency Constraint to the other side, the Vertical Constraint on the line segment onto which the Tangency Constraint was just applied becomes Redundant and the Solver Message instructs me to delete it.
After deleting the Vertical Constraint I have 1 DOF remaining, but the 8 mm Horizontal Constraint still isn't flagged as Redundant until I click the "(click to select)" hyperlink in the Solver Message.
After doing so, Sketcher notices that the 8 mm Horizontal Distance Constraint is Redundant.
If I try to recreate the Sketch from scratch I don't get the errors, but I'm probably not exactly duplicating the procedure.
OS: Ubuntu 18.04.3 LTS (ubuntu:GNOME/ubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
(dated 2019-08-21)
Build type: Release
Python version: 3.6.8
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)