I just killed Iron Juggernaut and Tyrande never showed up to open the doors after the fight. Baine and Vol’Jin ran up to the door, but it stopped short of Tyrande jumping in. I encounter this bug with some relative frequency, maybe 1/3 of the time or so? It could be less than that, but it is persistent. Leaving and resetting the instance does not fix this problem, I usually have to wait until the next reset to just reclear it. Please just add something to click on the gate or something to open it. It’s already pretty frustrating doing SoO for those stupid shoulders, I’ve been doing this for years and that little change by adding a toggle would really take the sting out.
Still happening in 2023. 
still happening in 2025
Because you’re still breaking it.
Wait for the RP to finish behind the Juggernaut before engaging it. You only really have to make sure it dies after the final line has started being said, but since people are impatient and tend to kill it in one shot that’s not really enough wiggle room to guarantee you still won’t jump the gun and break it again.
The scripting for the zone was designed with the understanding that this fight would take multiple minutes to complete - long enough that even if an entire raid group was somehow organised enough to engage as soon as is possible they still wouldn’t have cleared it before the RP was done. Attempts to go back and change the script runs the risk of breaking things differently (see Westfall Story in the Return to Karazhan).