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.
Devices History
Htc Elf-Htc Google Nexus One-LG Optimus 2X-Samsung Galaxy S2-LG Nexus4

"Simplicity is the ultimate sophistication."
"The greatest ideas are the simplest." William Golding
"Simplicity is the art of maximizing the amount of work not done." - Agile Manifesto
"Simplicity is the way a human/developer should think to easily solve problems." - Wulsic

My Work So far