I can’t get it to happen every time, but I’ve definitely been able to trigger it multiple times. This time, I got a toon to just before a new level (2 xp away), then, while sitting in an asteroid field (don’t know if that effects it), I use the Character Select option from the side tab, and that seems to be the thing that triggers it. I can’t prove it, but I think it only happens when you have multiple toons.
I’ve tried returning straight back to the original toon, logging in as the other and back, and every combination of choosing toons that I can think of, and it’s triggered a few times but not in a way I can say definitively “I did this set of things and it happened.”
Will keep trying, but wanted to report that it happened just before a level up this time, but it still seems to be something with the level up checking code.
Edit: And just to add, it always happens upon clicking the “Character Select” button, that is, as I’m leaving a toon it will trigger, not as I’m logging back in. I just exited/entered on a single toon about a dozen times (using Character Select, not logging out), and it triggered perhaps 3 times or so, but somewhat randomly.