Wire it. One ethernet cable ends this permanently, and everything below is what I would do only if a cable is impossible.
Why AVRs in particular? Because they are routinely the worst-connected device in the house. They sit in a cabinet, behind a TV, far from the router, with an antenna the size of a matchstick, and then they are asked to hold a steady stream while the phone in your hand shows four bars. The phone is not the AVR's problem; the cabinet is.
The order I fix it in:
Wired first. During interiors there is no excuse: a network cable run from router to rack costs less than one evening of frustration. After interiors, a flat cable along the skirting is still cheaper than any wireless gadget.
If wireless is unavoidable, look at what the AVR is actually connected to. 2.4 GHz through two brick walls versus 5 GHz with line of sight is a different world, and most AVRs default to whichever they saw first. A mesh node placed near the rack, with the AVR wired to that node, is the next best thing to a proper cable.
Contention. The family's devices hammering the router during your listening hours is real, not paranoia. Four phones, two laptops and a TV downloading an update will starve a stream. Some routers let you prioritise a device; use it.
Prefer the AVR's native streaming (AirPlay, Chromecast, the built-in service apps) over Bluetooth. Bluetooth is the least robust link in the house and it stutters the moment the phone moves or the pocket closes.
Firmware. Streaming stacks are the one part of an AVR that actually improves with updates, because the services change their ends constantly.
Dropouts that survive a wired connection are unusual and mean something else: a failing switch port, a router that needs a restart, or an ISP issue upstream. Message us the model, how it is connected and what the router is, and we can usually name it.
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