I can only second what has been said before - it does sound as if the electronics are failing.
Unfortunately Smok doesn't have the best of reputations for reliability nor longevity - though they do ship vast ammounts of products and do monopolise the shelves of physical Vaping Shops in many many areas.
While they seen to work fine when new, they seem to go off song more quickly than other brands.
I've been using Eleaf's iSticks since I started vaping in 2015 and only had to replace mine this year, so frankly I wouldn't go past this brand.
Whatever you decide to try next I'd say, do a bit of research first and then opt for an alternative to Smok.
Good luck!