Intermittent stability issues with new router

A couple months ago I received an email from Xfinity offering a new router for my service. I feel like I made a mistake accepting it. It has intermittent lag spikes consistently. Hasn’t stabilized in weeks. An internet stability test shows a ping spike up to 160-300 every 30 seconds without exception. The Xfinity support bots claim the connection is healthy. They’re seeing max speed, not stability. It makes every type of streaming, voice chat, or game unusable because it’s so unstable. The old router didn’t do this for 3 years.