Ultegra 9-speed will work with either a double crank or a triple crank. The front derailleur in the sale package is for the double.

Have you tried flushing out your 105 shifters with WD40? Sometimes this can work wonders on STI shifters. The old grease becomes hard with age and combined with dirt can cause lots of shifting problems. Also look for t small screw on the underside of the right shifter than may be loose or missing.

Al