This is happening to my ios device and my W10 laptop. So in some circumstances, it happens to other devices.
Edit 1:I was able to sign in to MC on my ios device. Yet I still can't sign in on the laptop, I forgot to say that the issue is not occurring on my brother's Minecraft, it's only occurring to me.
Edit 2:I am now able to sign into Xbox live on the laptop. Yay!
It affects 1.14 as well, same with the hotfix. It should be fixed.
It is resource pack based, the bug occurs when you apply any old out-of-date resource pack. I know this because I tested old and new resource packs, and only the new resource packs make the capes appear as normal.