DIAGNOSIS: This is a classic SonosNet vs. standard Wi-Fi conflict. The Arc is probably battling between your home Wi-Fi and the Sonos mesh network created by other speakers.
FIX: Commit to one network. The most stable fix is to wire one Sonos product (any one, not necessarily the Arc) with an Ethernet cable. This creates a dedicated, rock-solid SonosNet mesh that all your speakers will use, bypassing your home Wi-Fi for speaker communication. The dropouts will almost certainly stop.
IF THAT DIDN'T WORK: If wiring isn't an option, in the Sonos app, go to Settings > System > Network. Make sure 'SonosNet Channel' is set to a specific channel (like 1, 6, or 11), not 'Auto'. This prevents it from hopping onto a channel suddenly crowded by your router.
HEADS UP: If you have a mesh router system (like Eero, Orbi), avoid using the 'Wi-Fi Assistant' or similar features that try to optimize connections—they can kick Sonos off the network. Set up a dedicated 2.4GHz SSID if possible.