Once i had submited the tmq quest ( only have seen it by tmq1 fuel) the bagpack doesnt disappeared. i could not throw it from my back to the trash i had to put it first in the inventory and then i could throw it away. I was scared a bit haha because it was still in my bag as i wanted to do ud1 but it didnt work for me. My party members joined ud1 but me not. I even re loged and the bagpack doesnt diasappeared, until i knew how to put it away. And then ud1 worked for me. Imade experience with such a similar bug with this "bagpack bug" if i remember i will report it. I think this "bagpack bug" causes many issues .
That is same as it was on ''retail'' ,first move it to inventory then throw out