I wanted to say welcome to the forum!
My question, and I am the least knowledgeable about the tech aspect around here about hot tubs anyway, I'm not sure if you are saying the tub is staying at an actual temp of 104 and/or the set pont is staying 104.
Are you saying you turn it down to say 101, you see its set to 101, but it a second or two the display goes back to actual and that is always 104?