90's Sundance Calypso chugs, and trips circuit on Cleaning Cycle. Lists FLO message.

Hi, my hot tub has a fairly new heater, and a newish United Spas C5 box/thermostat. It started making mystery noises during the cleaning cycle, but the jets would still work. Now it's stuck on shutting down right away since it's programmed to do the cleaning cycle next. It comes on for a few seconds, shows the FLO message, starts making a chunking noise, and then the circuit shuts it off. I've replaced the filter, drained and cleaned the tub,looked for obstructions in the pipes I could get to, it still does the same thing.

Can you help me solve this puzzle? Any ideas? Thanks so much!

It sounds like your pump and motor is having an issue. It is going into flow because pump is shutting down before it should. I don't know if they may have been something in the pump causing the noise and now has locked it up. Or if the motor is just locked up now.