AirPlay is great, but problematic if it stops working -- because it doesn't generally toss any user-decipherable errors. If your stereo gear crashes while playing some tracks from your iTunes library, here's how you can probably fix it.
While AirPlay receivers can sometimes randomly crash for an assortment of network-related reasons, a more likely cause is a malformed album art cover -- or an incompatible one.
Some Sony, Denon, and Marantz stereo receivers crash when they experience an AirPlay track when it can't properly interpret the graphic. The crashes are limited to receivers that have a display beyond a text crawl on either an attached display or on the front panel capable of displaying the album art.
The crashes can be as light as the playlist stopping, or as severe as the receiver locked in a reboot loop necessitating unplugging it from power.
If you're getting crashes with AirPlay, in all likelihood, you've got a file from a source outside of Apple Music with a really massive graphic attached. Here's how to fix it.
Optional but strongly recommended: Back up your iTunes library
Dust off that 1TB drive you've got somewhere about the house, and copy the entire iTunes folder to it -- just in case something goes very badly.
If you copy the entire iTunes music folder, it retains all of your play counts, and locally stored playlists without relying on Apple Music or iTunes Music Match to rebuild.
For whatever the reason, if you want to use this library, hold down the option key when you launch iTunes. It will bring up a dialog box allowing you to select a different iTunes library folder.
If you're inclined, you could point it to the copy of the library you just made.
That out of the way, let's get the AirPlay crashing problem fixed.
Option 1: drastic, but probably comprehensive
If you don't mind eradicating album art and possibly other tags that you've applied, you can get new album artwork from iTunes.
Open the File menu in iTunes, select the Library sub-menu, and choose Get Album Artwork
Select Get Album Artwork.
This process can take a while, depending on the speed of your drive, and your internet connection. Be patient.
Option 2: Flag what tracks are crashing your AirPlay receiver, and fix it
Find the abberrant track in iTunes. Odds are, the entire album needs to be fixed. Select the entire album by shift-clicking the first and last track, or choose Select All from the Edit menu. Get Info by either hitting command-I or selecting Song Info also in the Edit menu.
Choose Edit Items
Select the Artwork tab. In the case of this album originally downloaded from game developer Bungie's digital store, the artwork is 1600x1600, and it crashes our Denon AVR-S900W every single time.
You can select the art and hit the delete key to eradicate it completely. Another option is to drag the artwork out of the album art field and into whatever image resize tool you see fit to use. After you've crunched it down to less than 600 pixels square, drag it back in, and click OK.
Depending on how many tracks you're fixing, and the speed of the machine overall, iTunes may chew on the addition for a bit. After the process is complete, the problem should be fixed.