There are two errors that need to be addressed in this pattern. The first is in the setup row of the back.

Row 1 should read thus: (the additional sizes were accidentally left out of this row)

Row 1: k2, moss 5, k1, pm, k7(9, 11, 13, 15, 17), pm, k2, moss 5, k2

The second is in rows 1-10 of the short row shaping of the back armhole:
Here is the corrected set of rows.

Rows 1&2: K2, moss 5, W&T, Moss 5, p2
Rows 3&4: K2, moss 5, k1, working wrap with wrapped stitch, remove marker, W&T, P1, moss 5, p2.
Row 5: K2, moss 5, k to marker, remove marker, k2, moss 5, k2,
Rows 6&7: P2, moss 5, W&T, Moss 5, k2.
Rows 8&9: P2, moss 5, p1 working wrap with wrapped stitch, W&T, K1, moss 5, k2.
Row 10: K the k sts and p the p sts, taking care to work the final wrap with the wrapped st.

To Fit Chest Measurements: 32 (34, 36, 38, 40, 42)”

Yarn: 9 (10, 11, 12, 13, 14) balls Valley Yarns Superwash DK (100% Extrafine Merino Superwash, 50g/137yds) color 18 Classic Navy

Needles: US 4 (3.50mm); 7 (4.50mm)

Other Materials: twelve 5/8” buttons

Gauge: 22 sts and 30 rows = 4” in stockinette stitch with larger needles