All Android compiles of GreKo used to cause problems to me since v12.5 on which Rapidroid is still stuck. GreKo works fine in xboard mode if you choose fixed time per move setting but Fischer clock will not work as expected because the engine uses always 2 seconds/move.
Starting from 12.6, all successors of 12.5 used to hang on move in the middle of the games several times, causing my tournaments to be interrupted. That's why 12.6, 12.8 and 13.1 could not be introduced.
I hope 2015 version will be more compatible so that i can rate the improvement.
You may give a try with Greko 2015 for Android: HERE