Original post by: annesaladar ,
This happened when i had zte zmax pro brand new. I installed all my desired app and factory phone app stopped working. I tried the clear data thingy on the phone and contact and worked after reboot but it happened again after 1 testcall. Did it again and same issue occured. So I end up doing the factory reset and so far, after 3weeks of fixing it, i never encountered it again.