The pieces “Sonata in G for Piano and Violin, K. 379” and “Sonata in B-flat for Piano and Violin, K. 378” are ungrouped but Musicbrainz shows the grouping correctly for disc 15.
In addition is the grouping also missing at Mozart 225 Complete New Edition:
Disc 15 - Sonata in F for Piano and Violin, K. 377
Disc 15 - Andante and Allegretto in C, K. 404
Disc 16 - Sonata in F for Piano and Violin, K. 377
Disc 16 - Sonata in E-flat for Piano and Violin, K. 380
Disc 16 - Andante and Allegretto in C, K. 404
Disc 18 - Sonata in E-flat for Piano and Violin, K. 481: 3. Allegretto (con variazioni)
Disc 19 - Sonata in G for Piano Duet, K. 357
Disc 19 - Sonata in F for Piano and Violin, K. 547 “für Anfänger”: 3. Tema (Andante) con variazioni