Change 315900 had a related patch set uploaded (by Nikerabbit):
ext.uls.compactlinks: add explicit dependency to mediawiki.jqueryMsg

https://gerrit.wikimedia.org/r/315900

Change 315900 merged by jenkins-bot:
ext.uls.compactlinks: add explicit dependency to mediawiki.jqueryMsg

https://gerrit.wikimedia.org/r/315900

The issues does not happen on all pages, and goes away when clearing local storage. At this point I have no idea how many people might be affected.

Change 315901 had a related patch set uploaded (by KartikMistry):
ext.uls.compactlinks: add explicit dependency to mediawiki.jqueryMsg

https://gerrit.wikimedia.org/r/315901

Plan is to try to SWAT the proposed fix on Monday.

Another report at https://www.mediawiki.org/wiki/Talk:Universal_Language_Selector/Compact_Language_Links showing https://commons.wikimedia.org/wiki/File:Chyba_u_kompaktn%C3%ADch_jazyk%C5%AF.png

Expanding mediawiki cll comment from yeryry:
[1:20pm] yeryry: Still happening on old Chrome, not happening on newer Chromium I just installed.

Change 315901 merged by jenkins-bot:
ext.uls.compactlinks: add explicit dependency to mediawiki.jqueryMsg

https://gerrit.wikimedia.org/r/315901

Change has been deployed in production across the full WMF cluster.

Could someone test that and confirm it works?

According @Josve05a, the issue has been now fixed. They still seen that on sv.wikipedia in the last two days. There is so some probability the fix solved that.

@Dereckson Thanks a lot for deployment and followups!