Cowork (Frontier) OneDrive/SharePoint document read errors

We've recently managed to start using the Cowork (Frontier) agent in M365 Copilot and some of the fantastic capabilities it provides.

We're seeing an issue where right now the agent it failing to read data from withing documents such as Word documents in SharePoint and OneDrive. 

We see errors in the detail such as "ReadFileContent tool keeps failing with auth expired" and "Auth expired. Let me retry - the system should have refreshed the token.".

Other agents appear to be able to access SharePoint/OneDrive content without error and people trying to access those documents definitely have full permissions (their own OneDrive as an example). Works when files are manually attached to the prompt. We've enabled model sub-processing which is the only dependency I can see for Cowork.

Wondering if a widespread known issue or something specific to my environment?