Below FL100

[Autothrottle]

Hello,

I have a question about the 737 PMDG
In descent, after having passed below 10 000 fts, the PA disengages VNAV and set LVL CHG automatically.
Why does it do it?

Thanks.

[Nexus]

My first guess it's the autopilot disengaging the VNAV because of the overspeed. Remember the aircraft is trying to slow down from 290kts to 240kts when passing 10.000ft If you're 15knots above the VNAV target speed speed (in your case 240 kts below 10.000ft) it will revert to another mode
For example: (LVL CHG + MCP SPEED + LNAV)

Solution: use the inflight speedbrakes, just for maybe 15 seconds. Maybe a tad uncomfortable for the pax, but You'll decrease the speed