My issue does not appear to be exactly related to this topic, but it feels like a good place to start. I'm using Logic 10.5.1 on a MBPro mid-2015 running OS 10.14.6 (Mojave).
I add notes to the piano roll.
I open automation (Note Velocity) in piano roll view and select the notes whose velocity I'd like to draw in.
When I try to draw a velocity line at any angle in the automation area (across the notes that I've selected), the starting point of the line always jumps to exactly one and a half measures earlier than where I click.
If I simply click and let go (without dragging), it draws a velocity line across all notes that exist in that previous measure and a half.
This only happens in my current project.