Hello,
the XPUIPC fix does not solve the problem completely. It seems a bit better but the climb and alt hold is still quite wobbly as the autopilot is unable to maintain steady speed and climb rate. It still tends to climb much too steep, lose too much speed, go into level or even descent, pickup way too much speed and go into another steep climb wobble. Alt hold is a similar story, constantly wobbling up and down around the selected flight level. If I remove the XPUIPC from plugins and start without it it's fine.
edit: Also I noticed that the FMC can sometimes create quite weird routes. For example the LSZH BLM2Z arrival to ILS28 with GIPOL28 transition generates a route with 2 very sharp points that "reverse" backwards instead of turning smoothly into the transition from GIPOL. I always have to skip the ZH203 waypoint and go direct to ZH204 from GIPOL as the FMC is unable to make a smooth transition there. I use the default AIRAC as Navigraph causes the Gizmo errors. This problem I mentioned is with default AIRAC (1509).
edit2: And also this happened when I just now tried to select different arrival procedure:
Gah! And the error completely messed up LNAV and autopilot both of which now refuse to engage.