Ranger – “Defense” [Campaign 5, Mission 3]

In versions 1.5 and 3.0, I would first capture all the castles, then release the heroes. The garrison was prepared last, after clearing the entire map and having all heroes visit all upgrade locations. The checkbox for releasing heroes was always checked immediately after releasing the second hero. I only released heroes using Faidaen.

Could this bug only exist in the unpatched version?