XAA is also testing CSC not main channel

USC isn't bound to specific U.S carrier butIts official U.S unlocked channel for unlocked devicesXAA is secondary channel.USC is the channel that is sold by samsung official as unlocked variant in US

More chance not to get one ui 8 update as well or security patchesIf this problem happens again, try USC

Maybe if you're using US simIt will automatically change the CSC according to Sim inserted.But can you provide me your device software info and build number

Have you tried to change CSC to USC?Come out of this theory and try USCIt will workThere's a long debate on it and i don't wants to get into itSimple change CSCIf you have XAA device with U firmwareSimple 