@Domenic:
Honestly, I thought you were joking when you said “I would expect this from a $25 device” — even a 4-station sprinkler controller with no network connectivity of any sort would cost more than $25…
Also, it’s unclear from your graph how frequently you are polling the unit. All that I see are messages such as heartbeat lost, heartbeat recovered, but how frequently are you polling? If it’s 1 loss out of 60 polls, that’s pretty normal in my mind.