That’s wild, I’ve never experienced that. That saving arrow is probably a side-effect of the lag, rather than a cause of it: if your browser lags hard enough the frequent ping-pongs between the server and your browser will fail and your connection will die and you’ll reconnect.
I’d be very interested to know if anyone else has run into this… I suspect that the “Improve how the eyedropper selects colors, so (for example) it’d be unaffected by Fog of War” item I mention in the roadmap I just posted would resolve this because the eyedropper would work via a totally different mechanism afterwards, but I don’t understand why it’s so slow right now for you.