[Client] Masteries descriptions missing

After the latest patch, me and some friends have had this issue where we go into our Mastery pages and if we hover through the mastery icons, we get the description text but every single one only reads: "Description unavailable". I have tried forcing the client to repair itself but it hasn't really helped solve this issue.

Now, since I don't know the mastery icons by heart, I need to configure my mastery pages by using an aid website where the tooltips actually come up correctly. It is quite annoying.

Has anybody else gotten this problem?

Edit: Created a video to show the bug. https://youtu.be/vDeb_8RkGxI