Migration assistant never finishes

I'm a dad with 8 kids and a lot of macs.

I bought a mini just to use as a "time machine server." I have several disks directly attached to that machine, and every computer in the house has two separate Time Machine backups saved on those disks.

EVERY TIME I get a new machine, I try to use migration assistant to move the data to the new machine, and EVERY TIME it fails.

The Mac mini is an M1 system with 16GB RAM, and it's connected to Gigabit Ethernet AND WiFi. (For some reason OSX really likes WiFi & bluetooth enabled, so it's enabled here.)

I just bought an M2 Air with 16GB RAM.

I have attempted to use migration assistant to migrate data from the M1 to the M2. The M2 is connected to gigabit ethernet and WiFi, too (with Bluetooth enabled.)

Four times I have seen the migration begin and then the estimate to complete grows until it gets to be over 100 hours, and the time still increases.

There is not a network or CPU bottleneck that would slow throughput and the migration never completes.

These systems are newer systems with AppleCare and it's not just one TM backup, it's TWO.

This has happened so many times when I get a new machine that I usually just end up connecting a USB drive to the old machine, running a brand new back up and then directly connecting a drive to the new machine to restore it.

What's the point in allowing TM over the network if it doesn't actually let you restore data?

I really don't think I'm overlooking something simple. I think that Apple really missed the mark on this.

Thoughts?