You cannot break inheritance for this item because there are too many items with unique permissions in this list. (4378392)

Many of these kind of below errors are being flagged from your ODM logs, indicating that ODM is experiencing difficulty in migrating OneDrive permissions due to a limitation posed by Microsoft :

Microsoft OneDrive reported fatal error while importing contents to target in batch 1505. Will retry in rerun. See details
You cannot break inheritance for this item because there are too many items with unique permissions in this list.
Resubmit migration packages for batch 1506 because Microsoft OneDrive reported errors previously.

This issue occurs when too large number of items are being processed at once in one ODM task, such that migration for unaffected items with permissions have been successfully completed, but not for affected items whose permissions which are unable to be set.

The root cause is due to a hard limit from Microsoft for having a maximum number of unique SharePoint / OneDrive permissions for items in a folder, library or list, so for your scenario, this maximum number has been hit, hence migration of more unique permissions is not possible now.

Kindly refer to this external Microsoft Technote for more details :

"You can't share this folder because there are too many items in the folder" error when trying to share or break inheritance
https://docs.microsoft.com/en-us/sharepoint/troubleshoot/lists-and-libraries/error-share-break-inheritance

​​​​​​​To workaround on this issue, please consider to :

1) Reduce the number of uniquely permitted items in a folder, library or list.
For example, to temporarily move some items at source out to alternate storage first, then migrate, lastly move them back.

2) For affected OneDrives where item reduction is not feasible, then they will need to be migrated in another brand new ODM Task with this selected option for "No Permissions".