Class change limit?

[Dan Maku]

One of my friends have found themselves stuck as a hunter trying to do a Client Order. Is there a limit on class changes now?

[TechnoV]

I don't think you can change while you're doing a mission, maybe that's the problem.

[Randomness]

Odd. I know some client orders require you to do them with specific weapons (and thus a certain class), but...