Error: Operation would change object type, which is not permitted.
Every incident of this error we have investigated so far has related to corruption within a mailbox item.
When available we will supply the folder name and subject line of the item in question so please check to see if the item is required or can be ignored/discarded.
Quite often it is still possible to open a corrupted item within outlook or webmail as the corruption relates to unseen areas of the item.
It may be possible to recover the corrupted item by copying it to a different folder before attempting to migrate it again.