I'm getting odd latency jitter:

I've tried multiple access points (Unifi, FritzBox), different channels, different SSIDs (longer, shorter, spaces, no spaces)
I can't quite pinpoint when this started happening.
inSSIDer suggests that I'm on the right channel (1):

Can anyone offer any suggestions apart from trying 5GHz, which I will do once I can buy a new AP that supports it..