Never seen this one before. Ping times on my LAN hover around 10ms, but creep up slowly from 7ms to 14ms and then jump back down again. It's kind of like if something was answering on a ~10ms timer instead of interrupt driven.
Of course, my other laptop on the same AP isn't doing that. And they're both Macs. Sigh.
ssh+2FA to all your machines, anywhere, without opening firewall ports.