I have the same issue, and re installing indeed fixed it, but just wanted to add a bit more info:
This has been a constant thing since around a month and a half. Every new release had that same issue and it used to fix itself after a couple days. A week after Blackhawk was released, it stopped fixing itself entirely.
Every newly released troop had the same issue, Gard and the new one, and all new troops from reward chests as well. Even last week’s weapon had it too.
Only play on android, I get the occasional download when firing up the game ranging from 2 to 30mb and have enough storage for it. Maybe it’s RAM related?
I’ve had this problem too - on Android. What fixed it for me (w/ out reinstalling) was to go to the application info in settings and clear the cache for GoW.
The app will re-download stuff again when you start it up (~30mb I believe, akin to what @Gungner said), but you save yourself the full re-download/install of the app.