It seems to me you have two UK language enabled in Cataloglanguage table. Make sure to check there. 

Hi Quan,

I checked in the CatalogLanguage table, and it just has one entry for UK.

See the attachment :

https://1drv.ms/u/s!Av-R4wFUrLuygYQqJ1bzffAnrNzBlg

Thanks,

Anurag

Does that happen with newly created node? Or just existing node?

I'm guessing (obviously) but you might have versions in old language (en-GB perhaps), then you change it to en-gb 

Where have you gotten those languages from?

I am not sure commerce will support anything but the two letter ISO language and region codes.

What I would have expected to see is languages such as 'en-GB' (english in great britain/united kingdom) and 'en-US' (english in united states of america).

As a matter of fact, Commerce supports both formats ;)

Any tip how I can sort this now?

Thanks,

Anurag

When it comes to data, I'd suggest to contact our developer support service and provide the information needed for investigation. I can technically tell you to try something, but it's not something I should do.

Including a region as UK that isn't a language at all? :P

I thought you were talking about "en".