PartDesign: Fillet breaks the model of a round pipe when applied to a beveled pipe end

### Problem description

When applying fillet to the edge of a beveled pipe, it completely fails to generate the model. Please see screenshots

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Additionally, for some reason the fillet fails when setting radius more than 12mm (see attached model for dimensions)

Found in weekly build, confirmed in safe mode

### Workbench affected?

Part Design

### Steps to reproduce

[FilletPipeReproducer.zip](https://github.com/user-attachments/files/26431429/FilletPipeReproducer.zip)

### Expected behavior

The fillet is generated without issues

### Actual behavior

It's inconsistent. After several reproduction attempts, the model either fails to generate after fillet is applied (as in screenshot), or the fillet just fails to apply completely. Probably depends on how I draw the bevel pocket sketch?

### Development version About Info (in Safe Mode)

```shell
OS: Bazzite (KDE/plasma/wayland)
Architecture: x86_64
Version: 1.2.0dev.20260401 (Git shallow) AppImage
Build date: 2026/04/01 04:43:57
Build type: Release
Branch: (HEAD detached at 33dcd31f5)
Hash: 33dcd31f5e2175e7dcdfd3caf1d9d86440919bfc
Python 3.11.14, Qt 6.8.3, Coin 4.0.8, Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.3.0, IfcOpenShell 0.8.2, OCC 7.8.1
Locale: English/United States (en_US)
Stylesheet/Theme/QtStyle: FreeCAD.qss/FreeCAD Light/
Navigation Style/Orbit Style/Rotation Mode: CAD/Rounded Arcball/Window center
Logical DPI/Physical DPI/Pixel Ratio: 96/109.201/1
```

### Last known good version (optional)

```shell

```