Issues with mouse input's stopping movement on XBSX ?

After starting the game using mouse and keyboard I can move around fine aim and shoot fine but when I press some of the function buttons on my mouse it stops my character dead and I have to depress and re press the movement key ? 

So moving forward or sprinting press mouse side button and the character just stops. It only happens with function buttons IE side buttons not usual mouse buttons. It's like it cancels out my keyboard inputs when they are pressed.