In terms of input, I just swipe up once normally and it pretty much always works. It sounds like your touchscreen might be having some relatively major issues. It might be the whole screen or just a few dead pixels. So it sounds more of a hardware problem and unfortunately that’s something you can only fix by repairing the device or getting a new one.
In terms of getting the launcher hit to land, this should be quite easy and straightforward as it is effectively guaranteed to hit after a ground chain with practically any character other than Peacock and Squigly who are a tad less reliable. But I don’t think this is the problem you’re having.
Is it anything to do with lag? Maybe your inputs aren’t being registered because the FPS your device is getting is just too low. Once again, a hardware thing, though you should make sure all your other apps are closed and that you’ve tried turning the resolution settings down to the minimum (including disabling lighting effects) if that is the case.
