As the title states, it’s possible to get the profile page activity feed to load the wrong language feed if you try to load two separate tabs with different languages.
I’m able to consistently reproduce the behaviour by opening the “viewing [Language]” drop down, middle-clicking to open another language in a new tab, then quickly clicking on a different language in the original tab. The new tab will load the page under the page routing of whatever language you clicked on, but will seemingly contain the activity info for whichever language was last requested (the one you click on in the original tab).
I’ve tested the behaviour across a few different user pages now, all of which do the same thing. I’m currently on Firefox, haven’t tested it on anything else.
It’s not a huge issue at the moment, but the more languages are added and the more people with multiple languages on their profile, the more often it’ll happen.
I know there are still issues with pages randomly switching to another language if you have another tab opened in that language, and the language logo is very often wrong. That I can say for sure. The activity bug though, at least I haven’t encountered it recently, so that may have been fixed.