Just want to mention a bug I'm seeing - it seems to have started in 10.4.6 and persists in .7.
When I make a summing track stack and record - usually in low latency mode - into the stack track lane itself (all the constituent tracks speaking), there is sometimes a delay of a hundred or so ms introduced to the midi recording. IOW, it's not the playback which is delayed; the MIDI is actually recorded late - with delay. But If I record to one of the constituent tracks there is no delay; if I then move or copy that region into the stack track lane, there is still no delay. The delay only happens when I record in the stack track lane itself. Weird.