It is hard to see the gasket strips in the second photo, Andre. I really doubt that the problem is either the difference in material or its thickness. How about where the strips meet?
Since replacing the gasket strips made the problem worse, it seems clear that this is where the leakage is coming from.
In the first photo, it looks like there are gaps at the corners where the strips meet. Usually pushing the material together at the corners is enough to provide a seal. But if not, then a little glue in those spaces might help. It seems silly to ask if the screws are all tight enough. But sometimes the thicker new material needs to be compressed by tightening a bit past the point at which the screws (or bolts) seem at first to be fully tightened, though we don’t want to overdo it
Also, the middle strip looks irregular. Is is lying flat and not rolled over anywhere?
Something else that is probably not a problem but than can cause leakage: Is there good spring tension on all keys? A weak spring can cause a loose fit of the key pad.