How to set the Trigger bar and seating the Release bar for proper safety?

As far as the trigger bar¹⁰  goes, and the rack tilting down, it is made to be very tight. So yes, the spring helps, but it does not set the release bar (11) in place. You must wiggle the rack up and down and push the trigger in to completely seat the release bar (11)

See section 4.0 – Usage in the manual – HERE

1- When moving rack between positions, ensure the release bar¹¹ is seated so that the trigger bar¹⁰ is flush with two cross bars^{12 /13} for vertical position and for standard carry position (Figure 14).

2- You MUST wiggle the rack up and down, and push the trigger bar¹⁰ in to fully seat the release bar¹¹.