I am trying to perfect the 3rd part of When Johnny Comes Marching Home movable power chord exercise on the rhythm track level 4. I routinely get scores of >40,000 and several times I got 'almost perfect! next time you'll nail it'. The timing accuracy graph shows that my timing is quite precise and neither too late nor too early, and my musical intuition is in agreement with this graph, as I feel and understand the rhythm of the song. My best result was something like 47,000 points. (Next time I'll nail! Seriously!)
After the Android system got upgraded to Marshmallow 6.0 my skill suddenly evaporated. When I play the same exercise trying to feel the rhythm of the accompanying song dozens of the chords are marked red, I get hardly 15,000-20,000 points, and the the timing accuracy graph shows that everything I play is way-way too early. When I try to *not* pay attention to the accompanying music and play just according to the visualization on the screen the sounds that my guitar makes feel off-beat and unnatural and quite obviously do not match the accompanying music.
Today I tried playing on my son's tablet (Lenovo A3500-F running Android 4.4.2 KitKat), and suddenly my skill is back. When I play paying attention to the rhythm of the accompanying song my chords are correctly marked as green and the timing accuracy graph shows that my timing is again reasonably precise and accurate.