Bend removes unexpected material on edge (not relief)

[kotarou3]

Describe your issue

See the differences between the "Extend" and "Bend001" objects below (1st and 2nd images).
"Bend001" ends up removing extra material at the top that shouldn't have been removed

This might have something to do with the "refine" option on the "Extend".
If I disable "refine" and select both of the resulting edges for bending, I get an unexpected hole instead (3rd image)

CAD file: spline-pocket.zip
(Note: same file as issue #537, hence has an extra pocket that's uninvolved in this bug)

FreeCAD version info + SheetMetal WB version

OS: Debian GNU/Linux 13 (trixie) (GNOME-Flashback:GNOME/gnome-flashback-metacity/xcb)
Architecture: x86_64
Version: 1.0.0.
Build type: Release
Python 3.13.5, Qt 5.15.15, Coin 4.0.3, Vtk 9.3.0, OCC 7.8.1
Locale: English/Australia (en_AU)
Stylesheet/Theme/QtStyle: unset/FreeCAD Classic/Qt default
Installed mods: 
  * ExplodedAssembly
  * sheetmetal 0.7.55

Put here any screenshots or videos (optional)

Normal so far...

(With Extend.refine: true) Extra material moved at top!

(With Extend.refine: false) Hole in the middle of the bend!

[kotarou3]

Side note: Why did I not use the "extend" feature built into the "Bend" action itself?
Because the "real" project I encountered this issue in has to use multiple extends to work around the lack of feature #214

[shaise]

Sorry about that, but indeed the calculations rely on refining the model, and might break when not. This is a limitation and a bit complicated to fix.