System Information
Operating system: macOS
Graphics card: Intel Iris 550
Blender Version
Broken: 2.90
Worked: 2.83 LTS, 2.91 alpha daily build 15afaa3db25a, but Im not sure if this is due to changes in 2.91 that need to be back ported to a 2.90 point release
Short description of error
Using the mesh mirror tool (ctrl-M) affects UVs in an unpredictable way
Exact steps for others to reproduce the error
Based on the attached .blend file:
press ctrl-m, then x to mirror the selected 4 faces on the x axis, UVs appear unaffected. then exit and re-enter edit mode and the UVs have for the selected faces have now changed