Sounds to me like something was going screwy in your board (and maybe was all along, IDK). Did you try the old batteries in any other mod? Maybe you've got some low level drag from the board where it's telling you okay-ish batteries are "too old" and now that you've got some brand new ones everything is going UP
but that is pure speculation on my part and if it's warrantyable I might do that, or at the very least take it to a vape store if there is an at all competent one near you to have them test some things and whatnot, I mean you don't want to vape on a slowly going bad board because once ONE thing happens it can be Just a Matter of time before like, it ALL goes wrong. But you mentioned a Smok mod so test the batteries in that and like, see what happens.. If Smok is telling you the batteries are fine and the other mod is doing strange little creepy things, well I would retire that mod and etc.
Good luck,
Anna