Here is a mini lesson on how understanding the relation between yo’s and decreases that match it. From reading posts from folks running into trouble while working armhole shaping within the lace pattern, I think this may help.
While working this lace pattern, there is a decrease (either k2 tog or ssk) to offset every yo’s (this keeps your stitch count correct every row of the lace pattern). If you look at the chart, you will see that on the right end, the single yo is offset by the ssk, and at the other end, the single yo is offset by k2 tog. The double yo’s at the center of the lace pattern are all offset by a double dec named s2kp.
The key to keeping your number of sts correct while working the armhole shaping is to pay attention to the sts you have decreased and see if you have enough left to continue the lace pattern across the entire row. So, if you BO 5 sts at the beg of the row, and within those sts you were supposed to work a ssk or k2 tog, and now you can’t because those sts are no longer there (have been decreased), do not work the yo that went with that ssk or k2 tog. Instead, knit to the next set of sts that allows you to work both yo and their matching decrease. The same apply if you decrease sts where you were supposed to work a yo, then do not work the matching ssk or k2 tog.
For example, if you begin the underarm shaping on row 7 of the chart, you will BO 5 sts, which means you won’t be working the first yo. So, instead of working the double dec (done to offset the yo’s on each side of it) since you didn’t work the first yo, you should work ssk there instead to match the single rem yo to the left of it.
The same thing apply at the end of the row, but reversed.
It’s a great help once you start understand the logic of it all, and being able to recognize the relation between sts, and what sts look like. It’s the key to going “ah, ha! I get it!”