Yes boars running around can glitch through stuff or even fall out of the map.

Try to use multiple walls. With a trench around the outside.

Inner walls make sure are at or below ground so they don't get pushed off the map trying to squeeze out.

it really can be a pain, I have kind of given up on taming boars until they are fixed. It can be hit or miss if you just have a bad map spot or insane boars.