I don't recall ever hearing that having the metronome on had any affect on dropped notes. The two causes I know of dropped MIDI notes are a too-small "Prepare Using" buffer in preferences (try the old default of 500ms instead of 250 introduced with X1), and loop recording with input quantize enabled (a bug). there's also a MIDI buffering issue when looping with MIDI FX in the project, but it doesn't cause dropped notes.
 
Hard to say whether this issue with gain has any bearing on dropped notes; I wouldn't think so, but the surprising linkage with soft synth buffering suggests anything is possible.
 
 

More looping playback info. I would prefer a fix and not a workaround.

Just tested this and looping playback still drifts even when the synth output is set to zero. Also, now I am getting crackles and pops on subsequent loop playback iterations. Didn't notice that before.

Hi Conley,
 
I'd like to take a look at the project you are referring to. Please PM me to work out the details on how to get the project. 
 

Hi Dan, thanks for the reply. I am trying to cut down the project file to a transferrable file size which still recreates the issue. So far, only the full project exhibits the sync issue. I will need somewhere to dump it if I can get a smaller project for repro.
 
As far as the synth volume - I have a B4 and EzKeys synth in the project set to -6db and -8db lower than 0. Superior Drummer 2 is set to 0 on the output.
 
If I can get a smaller project size to recreate, or not, I will let you know.

Guitarmech111
I have a B4 and EzKeys synth in the project set to -6db and -8db lower than 0. Superior Drummer 2 is set to 0 on the output.

Is that the 32-bit Native Instruments B4? There's a known issue with Bitbridge padding the audio with an empty buffer, causing it to render late. This could manifest while looping.
 
And just to be clear, it was audio track input Gain that was the issue before - not synth Master output volume or track volume.

yep, 32-bit B4 and thanks for the double check on the 'input volume'.
 
I will remove that from the equation and see if it gets better. I could probably just freeze the synth and not even worry about it... I will try that too.