I’ve been having the same issues. I spoke to apple about it at length, and the only thing they did was blame Black Magic.
Here’s what I have figured out. Insert editing works infrequently, and it does seem that it’s luck of the draw.
I have had better success when the deck is connected directly to the Final Cut with no router in between. I’ve had more success with a DVW a 500 deck as opposed to a 2000 deck. For what it’s worth, if you choose entire Media when you’re laying off in insert mode, the layoff works fine. Doesn’t really help, for a quick insert, but it does point out that there is a bug…
Got a lot of people trying to figure this one out…. will let u know if I hear anything.