Okay disregard my previous message. I was looking at stress, and that looked okay, but displacements were unsymmetric.
The results in your model are unexpected indeed. You should send this to support, they should work with this to improve the software.
A workaround I found is to set the max element size on the pressurised surface to 10mm.
But a simple model like this should not have such bad results using standard settings!