Need "Loot Larceny" mission (Secret Armory DLC) in PT2 (PS4 GOTY version)

Anyone near doing the “Loot Larceny” mission (Secret Armory DLC) in PT2 (PS4 GOTY version)? It’s the one where you have to beat Knoxx. Mine glitched out! Apparently, if you also have the “Super-Marcus Sweep” while doing Loot Larceny, it’ll complete the Sweep mission & leave you stuck being unable to enter the area where you turn in Loot Larceny.

Was so looking forward to farming Craw but unless I complete this, all my time will have been in vain. Any help appreciated. My PSN ID is bevross – if you message or send friend request please mention it’s re: the Knoxx fight (PT2).