First off, what are you using to measure your humidity?
Analogue hygrometers are known to fluctuate wildly.
Secondly, how long is it staying at 80%? Is it a constant 80%?
(Again, analogue hygrometers are not always very accurate).
But if it is simply spiking up to 80% every time you mist the cham, then that is normal. It is not uncommon for the hygrometer to go up even higher than that during misting sessions (especially if it gets wet).
But usually that spike of humidity goes down pretty quickly as the cage dries out. What you actually want to keep an eye on is the average humidity throughout the day. Live plants in the cage help to stabilise the humidity so that it doesn't fall off so quickly from those spikes during misting sessions.
i got the exo terra hygro and i got a lucky reptile thermo and hygreo meter befor i misted it ws just 60 just checked aint hardly moved from 80 he seems ok is sleeping in mid of cage too.cnt really open up cage to put my other meter in there to c might wake him.he is hardly stressed seems ok always light colours