Unexpected Behavior Shifts in Rhino 8.20?

Hello everyone,

Since version Rhino 8.20, I’ve noticed some unexpected behavior that I can’t fully explain. Specifically, I’ve encountered increasing inconsistencies when using tolerances in certain functions the results are no longer consistent.

For example, in the attached file, the merging of faces behaves unpredictably. Sometimes the result is a valid Brep, and other times it’s invalid. In one case, I baked the merged part in Rhino while it was valid, internalized it, and upon restarting Rhino, it became invalid again.

Merge_Example.gh (346.1 KB)

I’ve also noticed behavioral changes in TryGetFiniteCylinder and the Unroller in combination with Rhino.Compute.

I’m currently running Rhino Version 8 (8.20.25157.13002, 2025-06-06) on macOS.

Did something change recently besides the shift from .NET 7 to .NET 8?

Is anyone else seeing these issues, or am I the only one?

Thanks already in advance!