Repro
{{unity command set_import_settings --asset Assets/Sample/Panel.png \
--settings '{"spriteBorder":
{"x":130,"y":210,"z":130,"w":110}
,"spriteMeshType":"FullRect"}'}}
Observed
{{applied: ["spriteBorder"]
unknown: ["spriteMeshType"]}}
The command reflects over TextureImporter members. spriteMeshType is on TextureImporterSettings. A sliced sprite needs FullRect, so the half of the write that lands gives a sprite that renders wrong.
ExpectedReach TextureImporterSettings members: spriteMeshType, spriteAlignment, spriteExtrude.
AI Kit today: aikit_set_sprite_border writes border and mesh type together.