During the summer we often get hot tubs over heating or will not cool down. Don’t worry. This is normal. The industry even have a term for it – “Thermal Creep”
So why does happen? Well the clue is in the name-Hot Tubs. By definition they are manufactured to be hot. They are not made to be cooled down. So, the problem occurs during the summer with lovely hot weather and spas and hot tubs outdoors in the sunshine will often over heat. So if your hot tub temp is set to 38 it might creep up to 40. Or if you try to set it at a low temp it will struggle to go down. This is normal.
So what can you do about it? Well not much really. You could add some cold water with a hose. You could leave the cover off. You could remove a side panel but I wouldn’t recommend it. I think you need to live with it. Don’t worry. We live in the UK where the colder weather will return sooner than you think!