Continuing with my "Seriously, Fsck X" theme... Seriously, Fsck #WordPress, and especially the plugins.
Why the actual fsck would a plugin need to save into the db what the domain of the website is, instead of taking it from WP_SITEURL or WP_HOME?
I mean, what is wrong with you, Frédéric Demarle, author of Polylang plugin? Can you reconsider your choice to become a WP plugin author?