Six years ago, Bug T44961 about unwanted spikes had me not do a loop
slide if the angle was too extreme, to avoid unwanted spikes.
The current bug showed that that angle was much too big, and limited
desired behavior in many cases. Changing the angle from 0.25 radians
to 0.0001 radians (about 0.006 degrees) still fixes the original bug
and seems very unlikely to be limiting desired behavior now.
4886ed2863