I have a number of external users in an external users' permissions group, which has access to a specific library in a larger site. They don't have access to the full site. For most users this works perfectly, but some users get the following error:
Access Denied [...] does not have permissions to access this resource. [...] Issue Type: User does not have permissions.
I've checked permissions comparing an external user whose access works and a user whose access doesn't. They have the same permissions at both the resource (contribute), and site (limited access). We've tried deleting the broken account wholly via Power Shell and re-creating it, but no dice.
This is SharePoint Online.