Apparently I miscounted how many stitches I'd need for each repeat at the new size. After 15 rnds (1 1/4") of 120 sts in k2p2 rib (and one plain round) I started the first zigzag round and came out short on the first repeat. WTF?

I'd only allowed one stitch for the center decrease when I should have allowed three. Well, crud. The heck with it, I'm not frogging the ribbing again to add another ... 2 more in 8 repeats ... 16 sts. If I skip the center decreases on this first round and just do the increases I'll be up to the right number to go back to pattern on the next one. Yep, that seems to be working so far.