[GRO] Can't continue with treehouse upgrade after save

OK, so, my Sim was upgrading the treehouse with lights, when I had to quit the game, so I saved and quit. When I did, my Sim was almost finished with the upgrade. Sadly, after I reloaded the game, my Sim lost the upgrade interaction in his queue and I can't restart the upgrade, because I am told my Sim doesn't have the required parts. Of course, he doesn't have them. He already used them on the upgrade he ALMOST finished. Am I really punished for not being able to play the game through the whole upgrading process? I really don't want to go through all the process of getting the parts and upgrading, this time without even being able to leave the game while upgrading. Why is saving in this game so messed up?