All streaming devices should be hardwired with a ethernet cable, no wifi.
Sound United devices like Marantz can be very intolerant of a wifi connection.
Hopefully, you bought the Apple TV 4k box version which came with a ethernet port.
Any NAS should be hardwired with ethernet.
If issues persist after getting fully ethernet wired, update all firmware, try a different modem, etc. It is a good idea to not cheap out on the modem and router.

