This can happen when there are Network Issues. We can Pause and Resume the ‘Task’ that hangs, which would solve this issue.
Please refer below screenshots on how this is done.
Pause the Task
Resume the Task
If the issue is still not sorted, please follow the steps as indicated in the below FAQ.
https://support.apps4.pro/apps4pro-migration-manager-troubleshoot-general-task-execution-hangs