Are these track-like residuals expected in filtered Fink LSST alerts?

Hi, I am working with Fink LSST alerts and made a binary sky map of alerts that survived:

  • an ML moving-object-like filter
  • MPC matching with astcheck singleton mode at 30 arcsec

I used alerts from 2026-02-23 to 2026-02-26 in a 5 deg radius field centered at RA=150 deg, Dec=1 deg.

The image uses a simple local planar projection. Alerts were deduplicated by diaSourceId, and each surviving alert was drawn as a single white pixel with no smoothing or intensity accumulation.

The result shows a surprisingly large number of short linear track-like structures.

Is this qualitatively expected, or does it suggest that my filtering / known-object removal is still leaving many non-target alerts?

I can provide more implementation details if needed.
PNG attached.

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