Move to game folder, and put there at least 3 mods.
Open the game launcher.
Move to Mods tab, select only one mod from the list, right-click on it, select delete.
Now chose either first or second option (no matter, bug occurs on both) and you have finally reproduced bug (3-1=2, but launcher says 3-1=1 - there is only one mod remaining on the list instead of two).