You could try recalibrating your right Joy-Con via the Switch's system settings. Maybe the controller is just somehow calibrated badly. If the problem occurs constantly, I think there's a solid chance that's the case. My personal experience with Joy-Con drift is that it occurs randomly, usually right after using the affected stick, getting its movement stuck in whatever direction was last used.
If recalibration doesn't help, then it might still be some kind of drift. Maybe the reason it only happens in some games could be related to different dead zones. Maybe the drift on your Joy-Con only occurs in a small area around the neutral position, and maybe some games just use larger dead zones, just negating the drift in that area. Though honestly, if that's the case, I kinda doubt it's actual Joy-Con drift and I'd assume recalibration should fix the issue. As I said, when I had Joy-Con drift, it was usually the stick's movement getting stuck in whatever direction I used last, and it could be anything between subtle movement and large movement, so if all you get is just subtle movement into the same direction all the time, then Joy-Con drift sounds like an unlikely culprit and I do think it might just be a calibration issue.
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