Those are standard warnings associated with Drupal. You can ignore those.
Try a complete refresh by pressing Ctrl+F5.
If that does not fix it, right-click on one of those language labels, select
Copy image location and paste the result here.
They're back...
Don't know why... It's pretty weird isn't?
Try this (sorry I only have the English menu items):
Abrowser (Menu) Preferences
Then select the Privacy tab.
Click clear your recent history.
In that popup select a time range that goes back before you had this issue.
And in the Details below, untick everything and only leave Cache ticked.
That's good news. Usually when some website resources break for no reason, a
Ctrl+F5 refresh forces it to reload the resources instead of using the cached
files.
Press Ctrl+Shift+J and look for any errors.
You should also try a dist-upgrade.
I wouldn't worry about it too much if it happened only once. Are you still
getting that?
I suspect what most likely happened was the server took too long to respond
and your browser aborted the retrieval of those images. This could be because
the server had a temporary slowdown or because
