I have a Master Spa that has been the best spa we've ever had, but the last few days its show code LF which the manual says its persistent low flow problems and shuts heater down leaving everything else working normal. Manual solution is turn power off for 15 mins and back on. this has worked in the past but now only for 10 to 15 mins and starts all over again. Water level is right, jets flow great when on, anyone has any suggestions? Thanks for any help.