or he should watch at the build.prop or there is something edited or need to wipe data from google playstore or there is some xposed module which is causing it I don't know but if you edited a lot on that custom rom with kernel and like that backup it first don't go immediately to stock or else it was just wasted time for you. It could also be your dpi but I don't think that's it also wipe cache in recovery that might work.
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