Two devices acting up could be unrelated . . then again it could point to a particular software application installed on both that just isn't stable . . there's just no way to tell.
If it were me, I'd do a factory reset of the device and if that doesn't resolve it I'd look to install a factory image via Kies in order to start from scratch. If at that point with the device being completely bone stock after a full wipe the issue remains I'd send it in for repair.