The two-arm search compared its arms by the order of the space group each
had picked, but Stage B leaves best_space_group unset whenever no
candidate is eligible - no candidate had enough observed absences to
trust. That is not rare on the Lorentz-filtered arm, and for a systematic
reason: the filter removes the badly-measured observations, which is
where the weak systematically-absent reflections are.
An arm that confirmed 422 but stopped short of naming a space group
therefore scored order 0 and lost to an arm supporting P2, and the
demotion was logged as "taking the higher symmetry" - the comparison and
the message both wrong, in the one direction the design says cannot
happen.
Carry the point-group order in the result, set from the order Stage A
actually adopted, and compare on that.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>