>> I would say that they simply zero beat poorly.
I've seen a lot of cw ops at various field day setups set the i.f.
shift for a comfortable tone, and then tune to the s-meter peak,
which is usually not the same as the cw offset.
Also, the cw pitch control can get you in trouble if the sidetone
does not track with it.
And tone-deafness plays a part sometimes, I'm sure.
I've been fortunate not to have experienced any deliberate "grabbing"
of a run frequency as described in this discussion. I always assume
that they just couldn't hear me (lp<100w), and I move on. Or I switch
to s&p. No harm done. Keeps my b.p. down.
I analogize this to a "bump and run" move in racing - frowned upon,
but in the heat of battle it happens. And sometimes the tactic can bite
you back. Sometimes it's deliberate, sometimes accidental.