Sharepoint online token refresh fails

We’re trying to use a “always listening” pipeline (filepoller / salesforce subscriber), which will react to new events and write files to sharepoint online.

The pipeline is working fine for the first hour - after which it fails with the following error:
HTTP Response Code:401; Response Message: Access token has expired or is not yet valid.

The account is configured to automatically refresh the token based on the provided refresh token.

My assumption is that the account / access token is only read on pipeline startup, therfore we moved the “Sharepoint” step to a sub-pipeline (Batch size 1, pool size 1, do not reuse executions) - so the sub-pipeline is started for every document.
However, after approx 1 hour, the same error appears - so apparently the token is only read when loading the parent pipeline.

Can this be somehow “configured away” - or is this simply a pattern that snaplogic is unable to work with?