Entering Mission After Objective Has Been Completed - Fail For Other Members (Triton)

[Sanatori2050]

I was trying to enter a mission on Triton and I was paired with a group that had already completed the objective and the countdown timer was running. I came in with about a minute left and was in the reactor chamber and there was no possible way I could get to the extraction point before time ran out. I aborted the mission hoping everyone else would be able to complete the mission (not sure if they did or not) but I failed it and had to redo by myself. Since I thought that this particular thing wasn't supposed to happen, I'd let you know it still keeps happening, at least in this one situation.