not sure what you are doing here, but the seems not the way to toggle 2 nas devices.
- platform: wake_on_lan
name: (Wake) Synology Nas 1
etc....
- platform: wake_on_lan
name: (Wake) Synology Nas 2
etc....
Just create a dedicated switch for each individual device.
Also, the button should simply be listed in the devices entities, so not sure you need the extra serial data there.