I found out something shocking that could be related to this. AWDL, the proprietary protocol behind AirDrop, will exclusively use channel 6 on 2.4ghz networks and channel 49 (in the US) on 5ghz networks to find any nearby clients, and it’ll look for them about once a second. That means if your WiFi network isn’t broadcasting on those channels, any Apple device that doesn’t have AirDrop disabled will constantly be switching WiFi channels to check for this and switching back. I learned this when trying to get VR streaming over WiFi to a Vision Pro and found very consistent lag spikes once a second until I changed channels on my WiFi router.