But the flow of water into the spa is very strong like it always has been and the pressure is not running abnormally high. Restricted water flow would seem to me like it would affect both of those... no??If HLS is functioning properly then it says water is getting to 135. That means you have inadequate water flow through the hear exchanger and what little water is flowing through is over heating.
Lack of scale on SWG has no correlation to scale in the heater. If heat exchanger tubes are restricting water flow then water will overheat in heater.