That happened to me with a western mohair breast collar.
Horse always wore leather breast collars, one day used a different saddle that had a pretty mohair one and horse would not walk on, when asked to he would bite at his chest.
Took breast collar off and horse was happy to go on.
In the old days practically all horse were ridden in plain snaffles.
When you were riding one of the finely trained horses that went in a double bridle, that was like adding power steering to them, horses seemed to become way lighter and more responsive and generally happier in that more precise contact than they had been working with plain snaffles, as one dressage coach demonstrated for us.
My soapbox on keeping horses comfortable in their tack around the head is, fit bridles where when they move from horse movement or rider using reins, the cheek pieces are not moving up against their eyes.
That is very irritating and distracting to horses.
Take videos and slo-mo or pause them and notice horses wincing as bridles jiggle around their heads.
The more loose-goose a bridle fits, the more apt it is to walk around their head.
Fit them well so they move a minimum and stay away from their eyes.
It all comes down to LISTEN to the horses and let them know we are doing so.