Hello.
I bought elite and then horizons on their respective release dates and then odyssey several months after its release.
all bought via the frontier store, in that time i have never had to reinstall any version but every other update i:e Huge, small or even hotfix requires one or two retsarts after the update bar fills and says sync files <1min. some times hours have passed and i have read dozens of support pages.
Everytime and i do mean everytime the solution has been cancel the update,
close launcher,
open default browser I:E chrome, opera,
Clear entire browsing history, download history and most importantly cached images and files, you can leave the other tick boxes empty,
RESTART windows.
Once windows loads start the update again.
for me this has worked many times since 2014.