So just to clarify, did you simply fast travel to each expansion area (Lego & Fortune Island) and install the content within game or did you do it prior to booting the game up from the Microsoft Store app? I just want to be absolutely sure about this before I make another move cause of fear that everything will just stop working again like the last time (that was a nightmare for me to fix).
I fast traveled to each expansion area and clicked Continue on them and it only said Install, I clicked it and it booted up Microsoft Store and installed only the expansion I wanted it to install and when it installed it worked correctly.