(RS) K5. P1. *K4. k2tog. K3 yrn. P1. Rep from * to last 5 sts. K5.
I am being extremely careful with this-my question is: Does every
row have to be completed fully before last 5 stitches?
I get to P1, and cannot get it in-go right from K3 to last 5 sts>
Same with some other rows.
If you are asking if you should be able to do the repeat all the way through before the K5 at the end the answer is yes. Your pattern is a multiple of 10+11. IOW the things you repeat between the *'s add up to 10 stitches being used and on either side of the *'s the stitches add up to 11, 6 at the beginning and 5 at the end. So you should be able to work the 6, then repeat the 10 across (completing the last repeat), and have 5 left to knit.
It works that way all the time (I didn't look at every row, but quite a few), you do the 6, repeat 10 across and finish with 5 and they should all fit in there perfectly.
Count your stitches and make sure you have the right number to start with. That can sometimes be the problem. You want 141. Then it is easy to miss something along the way. You could try putting stitch markers after every repeat and see if that gets you on track. Your 10 stitches between markers should never vary.