Thank you for your post.
It appears as though after selecting the materials and drawing the internal wall you changed to a different wall type then changed back to 'Internal Only'. The materials in the Wall Tool will only remember the common materials selected for the walls (e.g. plasterboard for Masonry Veneer will stay the same for the internal side of the Internal Only wall). Would you be able to please let me know if this was the process you took?
What I would recommend to do is to right-click on walls that you want to use the same values and materials and select '+ WALLS > Create Similar Walls' then create the walls as normal.