I have the same problem.
However - I don't think there's a fix for it, as Salamanda (stoneharry) said to me. It's a core bug. If you haven't got the latest core, upgrade. If you have the latest, there's nothing to do I believe. Atleast that's what Salamanda told me.
You can probably fix through something very simple, like changing the arena season level from 70 to 80 or something, but i'm to lazy to look it up