This isn't any kind of official response. I just looked closely at the
trace file.
It looks to me as though the two events aren't symmetric.
In turn 69.6667 the lower right of the two markers is on the cusp of
entering the first of the two regions. By snapshot 70.000 it has
entered @ 84.8316 58.1335 with speed 0.0661 0.5827.
On the other hand, the upper left case is slightly different.
In turn 99.6667 the upper left of the two markers is entering the
first of it's two regions. This occurs @ 58.1701 83.2621 with speed
0.9327 0.1743.
Though very close, these are not identical conditions. The force
inputs to the corresponding pushers also aren't exactly the same. The
first (lower right) is 0.38 1.96 just after entry, but the second one
is 1.94 0.50 just after entry.
It looked to me as if it worked properly for this stretch of time when
slowed down to as slow as 20 times.