I tried but it didn't work. No imei. After that I tried some of the multiple ways of flashing imei with QPST but almost all guides are for dual sims, my phone is single sim. So I tried enetering imei in slot 1, both slots, and slot 2. Only time it got written was when I entered it in slot 2. But when the system boots the imei is there but it won't work. So again reverted back to lollipop 5.1.1. and girlfriend is using it like that for now.I saw that Ilvmyname already replied. My take on this is because the bootloader is already locked I would clean all and lock to try and get the phone back to stock condition.
Did you try? Did it work?