Oriented Minimum Bounding Box gives incorrect result.

[GeoEugeneK]

QGIS 3.12 / Windows 10
Lately I have been using Oriented Minimum Bounding Box a lot and found out it sometimes produces a totally wrong output. I guess the bug happens in the low-level part of the algorithm implementation as it persists with both QgsGeometry.orientedMinimumBoundingBox() method of Python API and when calling corresponding processing algo, regardless of the CRS used (tried with EPSG:3857, EPSG:32631 and WGS 84).

How to reproduce:

1. Use the following WKT geometry (EPSG:32631):
   Polygon ((-167581.30771802365779877 12253.1009764485170308, -169728.33899063381250016 11811.64286796574924665, -169728.21535189682617784 10929.38266212840426306, -169311.85422288533300161 10223.62778342491401418, -168260.27974171470850706 10709.01371703742006503, -159956.56253779400140047 12916.02958690263949393, -167581.30771802365779877 12253.1009764485170308))

2. Run QgsGeometry.orientedMinimumBoundingBox() on a newly constructed geometry or add the geometry to a Polygon layer (EPSG:32631) and use Oriented minimum bounding box tool from Processing Toolbox.

In both cases, you should receive the following result:

• geometry (WKT)
  Polygon ((-2326.23927114296566288 8046.58608674397964933, 5786.00995210356086318 12863.23406304659511079, 3714.32692187554675911 16352.38442974641657202, -4397.92230137097976694 11535.73645344379838207, -2326.23927114296566288 8046.58608674397964933))

• height: 4057.836968

• width: 9434.441435

• area (sq m in EPSG:32631): 38283425.227139

• perimeter 26984.556806

• angle: 149.300277

Some general QGIS info: