Super Marcus sweep help!

If anyone could please help me my son and I were trying to get a completion done for super Marcus sweep, A third-party went ahead and the blast door closed and we cannot finish the mission. Everything else is done in the game so it’s quite frustrating

From what I read in the other thread you’re on playthrough 1.
If this is the case it won’t stop you progressing to playthrough 2.
I may be able to help but I’ll have to check my saves.

Yes I’m still on the first Playthru, that’s the last objective I have to finish. I appreciate any help you can give me.