Earlier quoted context omitted.
Don't German UI conventions follow the convention of using infinitive verbs for commands normally? ('öffnen' instead of 'öffne'?) [the only exception I know is the adjective "rückgängig" for "undo" ] Though even there your point still stands - they can be easily distinguished from the perfect form ('opened' (geöffnet) vs 'to open' (öffnen) ). So I guess I'm nit-picking a bit.
Native german speaker here. Have no clue about UI conventions nor grammar, but I'd expect either "Öffne Ticket" or "Ticket öffnen". "Öffnen Ticket" is wrong, just as "Ticket öffne". I suppose the Flixbus app was made by native German speakers coding in English language. That would explain why they chose "open ticket" rather than "view ticket" or similar. As some of the parent posts said, you also "open files" here, s…
It annoyed me more than it should that Word for Mac for years had a menu command "Beenden Word" (Quit Word) where the order of the words was obviously hard coded...
Or how Siri says "In 50 Meter Sie haben Ihr Ziel erreicht." (it should be "In 50 Meter haben Sie Ihr Ziel erreicht")
In English you can just take the sentence "You have arrived at your destination" and prefix it with something like "In 50 yards", and it's a perfectly valid sentence: "In 50 yards you have arrived at our destination". It might sound a bit mechanical, but it's not wrong.
If you do the same in German, it just sounds very confusing and wrong.