It would seem converting to FLAC is there best option for us Meridian Users. Are you using makemkv to convert your Blu-rays? If you are can you help with what library you are using and what settings you are using?

Living Room Kit: 861v4+ID40, DSP7000, DSP5500, DSP5500HC, HD621
Bedroom Kit: F80
QNAP TVS-471, Roon, iPad Air2