Hi,
For the device with assignment error, please go to one affected device side, open Settings->Access work or school->info and click Sync, wait some time to see if the status will be changed.
However, if the issue persists, please check if there's any same setting we configured under Device Configuration. If yes, unassigned it the affected user.
Meanwhile, we can also check the MDM diagnostic log and event log to see if there's any finding.
https://learn.microsoft.com/en-us/mem/intune/protect/security-baselines-monitor#mdm-diagnostic-information
Hope it can help.