As user Wargo reported: "When no description in my language is available it uses the Wikidata's convention to add language name next to the label when another language (en) is selected. It is displayed incorrectly: language name is part of label link and without space between name.
Solution: move language name out from link or format&differ it properly.
Steps to Reproduce:
In this case, the quantity property is listed as "quantityanglais"
The Property should just be listed as "quantity" [this is the preferred result] or "quantity (anglais)" [if Wikibase code makes the preferred result challenging]