Thanks. Unfortunately, the development of this server source requires contingency changes into some of the Wz files. So, for people that want to keep pace of the server changes, the need of taking updated Wz changes into account is necessary...
Regarding your stated issue between the Mob.wz and the quest for 3rd job, there are actually no bugs there. I'm assuming you've ran into a client crash as soon as you've reached the boss area. On one of the updates, HPBar were added to the 3rd job bosses, and referencing UI images to them are depicted on the UI.wz. Provided the updated UI.wz is being used by the client, no such issue should happen.
Solutions for that would be either remove HPBar reference nodes from the Mob.wz or utilize the updated UI.wz that was provided.
Drop chances for 2nd job drops, noted! Thanks for the feedback.