Setup new MacBook Pro

You can if it doesn't move for 24 hours, power down. You may find though that the transfer is incomplete and you have to wipe and reinstall the destination the operating system to ensure all components such as preferences, libraries and bookmarks are moved over.

Keep in mind your destination should have more capacity that your original. If it doesn't you can get external storage for cheap, and install the operating system there, and use its migration assistant to bring data onto the external storage.

Migrations may fail because applications or drivers are significantly different from the source to the destination:

I.e. Catalina and later Mac OSes only support 64 bit applications and drivers. M1 Macs may not support all plugins found on Intel Macs and Boot Camp isn't supported at all.

Storage on both sides should be less than 85% full after the migration is complete.

I.e. say you have 1 TB on the original and more than 850 GB to transfer, you need a minimum of 2 TB on the destination.

Drives are in 128 GB, 256 GB, 480 GB, 512 GB, 768 GB 1 TB, 2 TB etc where 1 TB = 1024 GB.

Filevault frequently poses difficulty for migration. Make sure both sides do not have Filevault turned on.

I think the first question I'd want answered is how were you attempting to do the transfer?

There is more than one method. For instance failed copy and paste recovery will be different for failed Migration Assistant recovery