Thanks for all the help guys. I ended up fixing this by batch installing the entire 2.1 updates folder into RedNAND via FBI instead of PlaiSys, deleting the offending app(0) title via FBI in RedNAND, and then reinstalling just that specific CIA file again (all on the same boot). Rebooted to...
I downloaded the 11.0.0-33U 0004009B00013302 title as a cia, and installed it to the RedNAND v11 via FBI. Restarted to RedNAND via HBL for good measure, came right up, then kicked off PlaiSys again to downgrade to 2.1.
The downgrade reported success, but OTPHelper still isn't happy.
That...
Yep, RedNAND was 11.0, upgraded OTA via System Settings. The checksum for the downgrade files are good, as well as the MD5 checks done by PlaiSys on the CIAs - all pass. Did a factory reset on SysNAND before starting the whole guide, so there shouldn't be anything else installed on it, no...
I have restarted completely from scratch 3 times now, on 2 different microSDs from different manufactuers, both of which were formatted with SDFormatter beforehand. I get exactly the same result, it bombs out on the same title every time.
Downgrading N3DS XL to 2.1.0 to get OTP for install of a9lh. (Pialect guide, part 4, section IV, step 15).
Every run of OTPHelper after a successful downgrade with PlaiSys fails the One Click validation check. Always with "app(0) is in unmapped area", and always for the same title...
@The Real Jdbye, I thought about that and I have blank DVD's and Blurays but honestly after like 90 songs I just listen to it a couple of hundred times toss it out and burn something else or have like 2-3 CD's. Florida here the heat in the car tends to ruin the CD's after like a few months even commercial pressed ones don't last too long.