Hi savvyxeus,
Before answering your questions, may I first confirm the following information to avoid confusion?
1. What migration type are you using?
2. Do you have on-premises Exchange server? If yes, may I know the version of the Exchange server?
3. Could you provide the full detailed error messages via private message for further research?
I've sent a private message to you to request the error messages.
Here are the steps to see the private message:
1. Please go to your details section on the right side of the community site.
2. Click Private messages.
3. Click the subject title of the response to read the message.
Best Regards,
Aaron Yuan