Moving too close to anything higher than you causes auto jump. Walking down stairs with some empty space in one side? Jump. Walking into a wall with a 2 block section in view? Jump. Trying to navigate a town? Lets try to jump through the door of any house I attempt to enter or exit. It's like anything you approach within 180° of your front it just makes you jump like the zombies do while pathfinding. Horribly frustrating for touch controls since it's almost impossible to fight mobs and move.
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Touch controls? Does MCPE-52213 describe your issue?
Yes, sorry for making a mess but maybe hold down on the jump button to toggle auto jump?
Have you tried turning auto jump off?