Typically Exposure Preview works fine wide open. However, when stopped down to say f16 with subject matter in dim lighting, the option 'Exposure Preview > P-A-S' (vice P-A-S-M) should apparently keep the viewing (EVF or LCD) bright. Unexpectedly it doesn't, the view shows as being stopped down. Whereas, with a relatively brighter subject matter scene using f16, the preview stays bright (eg with the no exposure preview setting obeyed for manual focusing). Not easy to explain simply...
Searching - found this in <Leica CL / TL / TL2 / T Forum> circa 2018. I don't see the then described snatched frames stuff but rather that the Q2M just plain stops down which ignores the set option 'Exposure Preview > P-A-S'. Seems to behave as though I had optioned the default 'Exposure Preview > P-A-S-M' or just plain ignores the set option in dim lighting.
Experimented by setting 'Exposure Preview > P-A-S-M' directly in the main menu and also as a thumbwheel option but I imagine they both work as one and the same.
It's really not a biggie but if somebody could confirm this either as a bug/buglet/feature or just that I've misinterpreted how the Q2M firmware should be working 😉