Twizzling tongue !!!!!

[police9384]

My 11 year old Section D gelding has recently started twisting his head n twizzing his tongue out of the rightside ov his mouth. I thought it was when he wanted foooooddddd !!!! but he has started doing it quite badly now when schooling, hacking n lungeing. He even forces it through his flash.When he does this he switches off n won't listen..............any ideas what it might be? or how I can get him out ov it?

I have changed his bit and had the saddle fitter out....dentist in November.

HHHHEEEEEEEEEEELLLLLLLLLLLPPPPPPPPPPPPP