Lens

When at the load menu on 41.26 I am having trouble with an unmodded sandbox save that worked on the previous build. I am getting "A map is missing. Check that the needed mod is installed", along with a list of maps in red: Riverside, Rosewood, Muldraugh, and West Point. The "play" option for that save is greyed out as a result. It loaded perfectly fine in 41.24. To my knowledge this issue will arise in 41.27 as well, as mention of it is not in the list of bugfixes. Help?