BTU or EVR firmware - differences

[japitts]

My A12 was supplied by EE-UK and ran EVR firmware, but was recently repaired by EE's repair service which included a new SW flash. It's now running BTU firmware.

VoLTE & VoWiFi still works largely as expected (some network issues at present), but I am slightly surprised at a network-repair centre installing BTU not EVR SW. Hence my question - is there anything that the network-specific SW has these days, that BTU doesn't?

[jimmyk87]

BTU is unbranded UK CSC sounds more like they have replaced your phone rather than repairing it, firmware flashing cannot change the CSC only programs like SamFW are capable of this, I'm on EE and have found previously that I get worse signal using BTU rather than EVR

[japitts]

There were a few quirky air-bubbles under the screen protector that there still there on the device when it was returned... the fix was a motherboard replacement.

Otherwise I would have suspected the same. Hence just wondering what differences there are.