Altitude and speed differences on alternate static

[CenterlineT]

It seems the static system senses more ambient pressure outside vs inside the cabin.
I don't know if you have two static ports or one. If you have one port then the heavy wing maybe the culprit (the static port faces the wind which it will compensate if there are two ports one on each side of the boom or fuselage, but not with one port) . For that you may want to check the rigging and also do a weight and balance to make sure your heavy wing is either weight related vs control surface vs wing or tail boom misalignment related. That may solve both your problems.

[mshac]

If the normal static port has a restriction somewhere in the system, it will reduce airflow. This will cause a lower indicated airspeed, and a lower indicated altitude. VSI would show a lower rate of climb/decent.

[Mich3773]

This was a good question about something I had forgotten, even though it was posted literally right in front of me. See the picture! I tested it in low level cruise. Airspeed dropped by ~10 kts, altitude increased by 150 ft.