Issues with OneDrive Internal Sharing for a Few Users

I've got a situation where three out of 200 users in our organization are having trouble receiving sharing requests from their colleagues on OneDrive. We're seeing issues that range from completely blank Word documents to actual content, and when we try using the standard sharing option, it throws an error stating that the organization's policies don't allow sharing with those users. It's frustrating because when I switch to the classic sharing settings, everything works fine.

Here's the scoop:
- These users are full internal members and were onboarded like everyone else a year ago.
- This issue has been ongoing; it's not a sudden development.
- Despite testing with 5 different colleagues, these users can't receive anything through the new sharing UI but can still share files out just fine.
- All accounts are OnPremisesSynced, and classic sharing is working perfectly for them.
- The People picker function identifies all users without issue, but the error appears right after selecting a user and trying to send the invite in the modern UI.
- Running checks in the console gives me a vague "Error sharing" notification.
- There are no outdated attributes or sharing policies set up in the SharePoint Admin Center.

I even used Graph Explorer to troubleshoot, but everything appears normal. I'd appreciate any insight before escalating this to Microsoft. I'm okay with using the classic sharing for now, but I'd really prefer a proper solution.