Pro 1 Arpeggiator

I've just got a Pro-1 and I've noticed that when the arpeggiator is used, it will play through the keys held down just the once and then stops. It doesn't matter whether or not I use Up or Up + Down.

I would expect it would repeat until the keys were no longer held down.

Is it me? A bug in the firmware? A design flaw? A feature of the original?

I thought I'd ask before raising a ticket.

Firmware has been updated using synthtool.

Any help would be appreciated.