My party and I had been stuck in Charr form during the Jade Maw instance of fractals [how or why this happens, I don’t know]. As you know the Charr form prevents you from picking up things like banners and the all important reflect crystals.
However, by use of the Warrior elite skill Rampage, you can pick up the crystals and launch them at Jade Maw for the duration of the transformation. I don’t know if it works for other transforms, but it definitely worked there. Hopefully this helps anyone else in a similar situation.
Note: Defeating the tentacles causes them to withdraw and damages Jade Maw slightly. Save Rampage until the final blast where it causes a team wipe otherwise.