The per-image G/B/mosaicity fit used a plain L2 loss, so a few outlier
reflections occasionally dragged a frame into a bad optimum - a stochastic
(~15% of runs) per-frame mis-scaling that elevated R-meas and collapsed CC1/2
at low symmetry (the image-level CC1/2 half-split makes the damage look patchy
across shells, while the data is genuinely noisier). A Cauchy loss (3 sigma)
soft-downweights those outliers without a hard cut: MyoB 0/10 catastrophic
(was ~2/10), R-meas stable, and ISa improves on every test crystal
(EP0210 9.2->12.4, MyoB 12.5->14.6, lysoC 10.4->11.2, cytC 11.5->12.6),
most on low symmetry.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 4.8
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