Yeah, this sort of thing even happens in Spanish every once in a while too. :| It's a little annoying but at least it doesn't punish you for it.
Well the Spanish is just kinda for fun so I usually get up to my 20 XP goal and call it a day. It's probably like 10 minutes. I'm inching along on that one but I'm at 40% fluency according to Duolingo so I'm slowly getting there.
The Korean is bc I'm planning on moving to Korea for work before the end of the year so I've been doing that for 1-2 hours a day. I've been focusing more on books than apps for that though. I don't expect to be fluent before I leave but I'm trying to at least get a solid start.