I was able in the past to easily unassing a pdl active and burning license from, for example, an MX67C, and to assign it to another MX67C same Org or not, didn't matter.
Nowadays it seem a lot more not doable, getting error message, license just keep assigned to the original device, not able to assign it to another device.
I opened a case and Meraki says an active and burning license cannot be unassigned after the first 7 days (which i was able to do today on 2 different device that have older than 7 days active and burning license)
So what is the real call today about 1- unassigning an active and burning license from a device , 2- assigning it to another device, same model