Revit 2026 TM 2025 Problems with window materials

Hi,

I’ve been using Twinmotion for Revit for a few years and all has been great. With the latest versions of Revit and Twinmotion, I am finding that when I import the revit model into TM using the collapse by material option, the windows are randomly being imported with the wrong materals.

For example, I have a simple wall with three windows.:
All windows are IDENTICALwith a windowframe material for the frames and a glass material for the glass.
When I import the model into Twinmotion (using Open in Twinmotion), one of the windows is as expected (glass for glass and windowframe for windowframe). The other two use glass for both the frames and glass (so the both windows are a single glass object).

This makes no sense and it randomly replicates in existing projects and in clean, new projects, even with default walls and windows. I have even added, say a header to a windows family, applied a third material to the header and when imported, the header takes on the material of one of the other window elements, so the whole object (frames, glass and header) are the same material !

This has made the software completely unusable for us.

Does anybody have a solution, please?