I had similar problems. It was so bad the Z2 auto was not usable. The folks at cpap.com helped me troubleshoot the problem. it turns out I had a defective hose adapter. The hose adapter had a small hole in the side of it. Therefore, it made the complete unit function in a very bizarre way. The start pressure said 4 but it felt like 15. There was no relief on exhale at all. They are sending me a new hose adapter.
They had me disconnect the hose and place my hand over the opening with the hose adapter and turn it on. There was an obvious hole in the side of the hose adapter. When that small hole was covered, the machine worked normally and quite well. (not as good as my resman 11 but fairly close.) cpap.com is sending a replacement hose adapter. Until then I have covered the side hole with duck tape (of course) in order to get a feel for the machines appropriateness for travel.
Good luck.
Jim