I spent about 5 hours in total getting to specific part on the truth and reconciliation mission LASO SOLO that i saved the checkpoint to return later, anyway my high school bud asked me to do some legendary coop, so I was like sure, he started a new playlist and away we went,we saved to return later.
Later that day I was about to return to my LASO SOLO save and I noticed a strange notification that said I had data saved in a different playlist and starting a new playlist would mean I lose the progress I had stored in my current playlist (which was the legendary coop). The progress being here obviously your last saved checkpoint. Apparently your saved progress is not playlist specific (ie you cant have different checkpoints stored up) however that notification box telling me was not there when i was off host about to start the legendary playlist coop with my buddy that would have stopped me losing my LASO playlist progress.
Here is that box + my reaction finding out I lost my progress.