VW Polo new gas fields – now tailgate closes badly in cold weather

Hello, maybe someone can help me or give me a tip. With my polo (already 10 years old – but still good) I had the gas fields of the tailgate changed in late summer. 2 Stabilus Lift-o-Mat were installed. At first I was thrilled – but now I almost regret the change. As soon as it is a bit colder (goes already at about 5 ° C in the plus area) the tailgate closes extremely bad. You have to thunder down quite nicely to get it locked in. If you have this there nn has done a few times, then it is strangely as before. Has something been done wrong during installation (something to adjust etc.) Who knows advice Thank you