Game Dev: Collision Detection - Bounding Box

We cover a basic collision detection technique that uses bounding boxes.

[ProtonChicken]

I wish I had seen this video two years ago when I needed it for a final project.

[elenavalsecchi]

Great tutorial, however i'm finding some problems with the use of the collisionHandler. 80% of the time the collision between entities is detected, but there is still a significant amount of times where entities that should stop when colliding pass through each other without even detecting the collision. Could it be a problem of concurrency? Are there ways to solve or reduce this problem(maybe using locks or something)? Thank you for your time