NOS sticker kit lifting on edges

I’m refreshing my wife’s kart and just installed a sticker kit that is new, but older stock (updated a Praga from 2012 to 2017 design). Plastics were cleaned, prepped etc and applied without bubbles. After application, I sealed the edges with heat gun, but now some of them are lifting off, probably old glue is not that sticky anymore.

What do you suggest using to hold them down? Is there a 3M contact adhesive that works well for this?