You may be aware that iOS has an issue where mostly the center of the iPad Pro’s screen is non responsive to touch when the iPad is running an App that may be using a lot of RAM. Djay Pro is affected.
(Other Apps like: Apple Maps, Procreate, SimCity that use high RAM are affected).
With Djay Pro, I have to use the Apple Pencil to avoid non responsiveness while recording a mix.
iPad Pro 2nd gen
iOS v 12.3.1
Djay Pro v 3.1.4