What can cause an excessively large brake cylinder stroke?

You answered correctly. An excessively large brake cylinder stroke can be caused by a defective automatic slack adjuster or worn mountings on the transmission system. A defective slack adjuster does not automatically compensate for brake lining wear, increasing the distance the brake cylinder must travel. Worn mountings can create additional movement or play in the system, also leading to a longer brake stroke. Excessively high reservoir pressure does not cause this issue. Knowing the causes helps you spot and prevent brake system problems in the future.