PAWS was malfunctioning because flannel wasn't routing things properly, with error messages like:

Jul 08 00:32:12 tools-worker-1002 flanneld[30692]: I0708 00:32:12.654880 30692 vxlan.go:325] Ignoring not a miss: aa:b6:d6:8a:be:4d, 192.168.42.4

A restart fixed it, but need to figure out what went wrong *and* figure out how to fix it.