When using RetroArch Android 1.19.1 (the one that still has stylus support) on my Samsung ZFold 6 in open mode and landscape orientation, the lower touch screen area of the DS in the emulator appears to "lose" any input if I click and drag over to an area of the screen below the Y face button. This occurs in both MelonDS and MelonDS DS emulator cores, on both of the app's Nintendo DS and DSi on-screen overlays, and on any game I play via Nintendo DS cores. I am fairly certain that this is an issue with the overlay itself, as switching to a non-DS touchscreen overlay allows me to use the full touch screen area unimpeded, and I noticed that the "dead zone" seemed to increase when I manually scaled the overlay. My guess is that there is some invisible button element in that area of the screen that is "blocking" input.
I have attached a screen recording of me playing Ghost Trick with a dragging motion from my finger being "lost" as I approach the right side of the screen. I have also attached the app's log file from that session.

retroarch__2025_04_24__16_43_51.log