The filing paints a chaotic portrait of the months and years leading up to the A Line opening in April 2016.
The Denver Post reports a "safety critical software problem" at some crossings prompted the return of the guards.
The April 20 incident on the A Line that left 200 riders stranded dented the transit agencies' relationship, but decades-long deal will likely remain intact.
The board decried DTP’s lack of communication and questioned what steps the company would take to prevent such incidents in the future.
Internal disciplinary records obtained by CPR News show engineers have made dozens of serious mistakes in the last two years.
The hold-up is over the wireless system that controls the A, B and G lines’ crossing gates.
The PUC Chairman took issue with an RTD spokesman's comment about the regulatory process.
The two lines, which opened in 2016, have had significant technical issues with crossing arms that come down too early and stay down too late.
State regulators have denied a request that could have eventually led to the opening of the long-delayed G Line commuter train.
Aurora police say the driver may have pulled in front of the oncoming train intentionally.