Energetic tongue whilst ridden

My pony has huge tongue movements whilst ridden/lunged in a bit. It hangs out her mouth and in and out and salivers everywhere.

The saliva dries up quickly and she does it in her present bit (eggbutt snaffle) and past bit (three ring dutch gag). Flash doesn't work however tight.

She has had her teeth looked at and rasped etc

So, why does she do this and how do I stop it?? Thanks

This often gets started because of stress, stress on the mouth, mental stress. Once started it is very difficult to stop. Have you tried riding with a halter or knotted halter to see it it stops? If so perhaps consider a bitless bridle.