VE is setting the language in {{cite}} templates. It's setting it to en-US, en-GB and other flavours which are not recognized by {{cite}}. Also, these shouldn't be set if the language and wiki are the same languages. On enwiki, these errors end up in [[Category:CS1 maint: Unrecognized language]]
Examples are:
https://en.wikipedia.org/w/index.php?title=Chris_Harris_(Automotive_Journalist)&action=edit&oldid=688324259
https://en.wikipedia.org/w/index.php?title=Adam_Waito&type=revision&diff=685374219&oldid=685373324
https://en.wikipedia.org/w/index.php?title=Aijia&type=revision&diff=681819929&oldid=681818020