Rhino 7 hangs and replicates materials : reproducible

I have a simple model which worked fine with Rhino v4 and Rhino Render, but after upgrading to Rhino7 and nXtFlamingo 5.5, I find that Rhino7 is painfully slow when doing simple things like displaying the materials list and selecting objects. Sometimes the program hangs (“program not responding” dialog appears) for several minutes, while CPU usage spikes. This happens when nothing computationally expensive should be occurring (like selecting objects or displaying the materials panel for an object).
When I assign a Flamingo material to a group of objects it creates a new instance of the material for each object. See the attached screen capture. The “purge” command reports zero unused materials.
Is there an explanation for this?
Version 7 SR10 (7.10.21256.17001, 2021-09-13) Commercial
Windows 10 Pro x64, i7-4940MX CPU, 24GB RAM, Nvidia K5100M, all SSD.

Have you tried using Rhino Render instead of Flamingo? It is in Rhino 7 more advanced, and Flamingo is getting gradually phased out. If you do try out Rhino Render you should just use the Rhino materials.

I assume your current renderer is set as Flamingo. It would be good to know if that is the case.

thanks for illuminating me Nathan.
Makes me mad that I just spent $295 upgrading Flamingo along with Rhino. With Rhino v4, I could create a model, assign it materials, and then render it with either the built-in renderer or Flamingo.
With my recent upgrade I’ve found that you cannot create a model that renders with both renderers. RhinoRender cannot properly render Flamingo materials and the Flamingo renderer cannot properly render what they’re calling “legacy” materials used by RhinoRender. The PBM materials and plant library of Flamingo are more realistic than RhinoRenderer’s, but the program definitely has bugs.

you sent to this into tech yesterday- from what we can see, your model seems to have been created using v4 materials with an older copy of flamingo.

If you delete your materials, then remake them with NXT materials, does the performance and appearance improve?

fwiw, we are seeing a weird crash bug with this model, but are still researching to see if we can figure out what is causing it.

thanks for replying Kyle. I learned from Nathan Letwory that Flamingo nXT is being retired soon so if I were to delete all the materials from this problematic model I would use RhinoRender materials, not new Flamingo materials. I think the problem that causes the infinite loop of material creation and the memory leak is in Rhino though, not in Flamingo.