Are you not getting a Rhino crash reporter dialog when these crashes happen?
It would be useful if you could share your animation 3dm file (zipped up with any and all support files) with us so we can investigate and try to reproduce the crash here. You can do so confidentially using our upload tool. I have prefilled my email address so that I get notified when the upload is complete. Please put a short description and a link bact to this discussion in the comment text area so I know what the file is for.
edit: there were some fixes related to handling of materials by RhinoCycles in Rhino 8.15 service release candidate. It would be great if you could try updating to that to see if that helps with your project: Help > Check for Updates… , set update frequency to Service Release Candidate.