I dont think fix is the correct term as the only thing wrong with Cadillac is a lack of full size cars. Everything else is tops in design, performance and reliability.
I wish I knew the reason why the small Cads are not selling. I know they do not appeal to me as they are too small for my needs.
My only guess is consumer expectation from Cadillac is not with small cars or that segment is hyper competitive especially with that MB C class thingy that just came out.