MCP turn on/off logic issue is caused by new sim update patch. In 1.12.13.0 update, Asobo was changed their MCP logic code. I think this is the reason, but I believe they will fix. If they not, I’ll revert or fix MCP logic code.
Temporal solution : Before this fix, you can use FLCH button to turn off VLAV, and Heading Hold button to turn off LNAV. And then, press SPD or Altitude Hold or Selected Headings. Or…use speed and altitude intervention function.
and…787X autopilot model rework was temporary stopped because I think their default model works fine now.