Only fixed with a /reload, happens regardless of whether or not your class power is full when the game ends. Stacks on top of each other, so if you leave it long enough without a /reload, you end up with a rather blinding glow around the border of your class power. Have only tested with Rogue, but I imagine it's the same with Chi, etc.

Thanks - Were you using the beta (of KNP) or release?

This was on Live, 7.3.5, with the latest version from the Twitch client, so presumably release. Twitch says 2.15.6.

Appears to be fixed as of BFA.