Help please what would you do ..................

[MagicMelon]

Get a squirty bottle of water, squirt it at her butt when she kicks out. I did this with one of mine who started a little habit of booting the hind door (same idea), he was so surprised after getting cold water squirted at him that he stopped rather quickly

 

[RachelB]

My mare kicks when travelling. It's a balance thing with her, she's better in a herringbone lorry than a forward-facing trailer. The big issue with her is that her neck is very low-set and to balance she needs to stretch it out low. Itherefore have to tie her ridiculously loose so she can get her head as low as possible to balance. She also will kick really badly when she has travelling boots on, so I travel her in long brushing boots and over-reach boots behind, and travel boots in front - although it doesn't sound like that is your problem as he was travelling fine before.
I would hazard a guess that he's not happy travelling forwards.