Chosen Solution

I have error E95 or E96, before spending any money, I tried NTC sensor first, it worked for me.I removed the Plastic cover over the pump. There were two flow sensors which were easy to spot. They had shiny hex connections one on each side of the water flow. I removed these with a box or small crescent wrench and clean the bronze tips of the sensors with a soft bristle wire brush. The tips of the sensors were copper and after six months to a year they build up corrosion. It doesn’t take a lot to cause them to malfunction. You can easily spot the corrosion it’s usually green in color on the sensor tips. After cleaning, thread these back in and put the cover back on the pump and try your heater. Be careful not to cross thread when re-installing these sensors. This worked for me without spending a time. If this doesn’t work, you may have let the flow sensors go too long without cleaning and they/re damages. But don’t fret. The sensors can be bought on line from ThermoMart (NTC sensor categories).They run $6.50 - $10.00 each. Intex will tell you need a $350.00 replacement pump. Don’t fall for that. I’d try these two fixes first is your a brave do it yourself type person. Oh, and remember to unplug your pump from the power source before attempting this fix.I replace and wired the sensors in to the circuit, wrapped the sensor in electric tape and put it on top of the white plastic exit manifold (Not on the black heat Exchanger).The Spa has been running for hours with no error and the temp is slowly climbing all evening.What do you think about this sensor and other brands? which one is better?

It is fit and the thread size is M10 but don’t forget to use sealant tape

@seanmaz that really does not qualify as a question. You should make a guide out of that before it gets deleted https://www.ifixit.com/Guide/new

why can I not get 2 of the screws in on the base case

What is the thread size?