networking – Latency spikes regularly spaced on a OnePlus5 phone, reproducible on both ATT & TMobile

I’m seeing latency spikes consistently spaced. I’m using to check latency (also experiencing the issue with real-time apps). Normal latency is ~100ms, at regular intervals I experience latency spikes from 2-5x (200-500ms latency).

I have not noticed this problem before today, the most recent change is that I added a 2nd ATT SIM, so I now have two SIM cards (ATT & TMobile). I experience the same result on both networks. A restart of the phone made no difference.

Since I can reproduce the problem on two networks, the problem seems likely to originate on the phone. Is this familiar to anyone?

The results of the latency test are shown in the accompanying image.

enter image description here