Do you have torches or fire within 25 meters? They will frighten from a campfire within 25 meters. Torches frighten them also but at less distance.

I don't understand them going through stone. Its easier to put them an a pit you dig out of the earth and a roof is good cause mobs will attack them if they get the chance. I believe the wolves may frighten them, not positive about that but it is a possibility.

Basically boars should be away from anything else and kept in the dark, You can use light sources from mushrooms, cores, etc. Non fire.