Lagers need starters. This is why liquid yeast with lagers is so terrible for the normal home brewer that I would never recommend doing it. What you want to do is pitch 2 or 3 packs of yeast with a 2 or 3L starter. Alternatively you get 2 packets of try saflager yeast and pitch those. We all make this mistake. I have found nothing but trouble with liquid staters and liquid lager yeasts. If you have a starter all made, I would pitch what you got and throw in some S23. Your liquid yeast profile will dominate since s23 ferments extremely clean.
Once Mr. Malty told me to pitch 2.5G of starter and I laughed. You get great beer all the time underpitching, but lagers you can't underpitch by that much which is why dry yeast is the way to go. Also, do not save and crop lager yeast cakes. That stuff is notoriously contaminated.