Mine was a bit patchy at first but now seems to be fine. I came to 7a from an ole’ samsung s9, which was v reliable but in a different position (back) so it took some getting used to.
I’m using my thumb, because using a finger would mean going two-handed (prefer having it on the back tbh). I’ve only scanned one position, and I do find it’s finicky in terms of needing to be in a certain position; I also find I need to press down more firmly than I expect, and it pretty much doesn’t work if my thumb is damp or wet.
Maybe what @WhoRoger suggested will fix it, pls update the post if it does!