Note: all get/set steps are done on Advanced > Params for each device. Do not change any other parameters or make any changes to the device in other parts of the UI.
Go to the NEW device and copy down its NEW altid;
Go to the OLD device and copy down its OLD altid;
Set the NEW altid recorded in step 1 on the OLD device.
Go back to the NEW device and set the OLD altid recorded in step 2.