[HELP] Cannot Trigger Eelside Down Mission

Hello, 

I posted on this forum a couple of months ago with this issue and it got lost in the convos, so I am reposting it and hoping someone can help me out. I am playing on my Xbox:

I have been trying to complete the Eelside Down step of the Bag of Tricks mission from tour 2. I believe I caused the issue a couple of months ago when  I had to force quit the mission without saving anything. Since then, when I load the game and attempt to activate the mission, the purple waypoint marker disappears when I am 10m out, and I cannot play the line challenge required for the mission to be considered completed. 

I have attempted to fix this bug by randomly teleporting to players around the map, starting co-op/party, and restarting my system multiple times but this has not resolved the bug.