Gaps between rows--I switched f garter to stockinette on cir

#1

I started knitting a sweater from the bottom using all knit stiches on a circular needle. When I bound off the armholes, I switched to stockinette between the armholes (still on circulars) and now I have a weird pattern developing every third row. There is a long gap between rows every third row- it is very predictable - like a pattern, but I want evenness in my stockinette!

I recently switched from a combined style of knitting to continental knitting- but I didn’t change the way I was purling.

Or could it be weird tension from the circulars?

Any help you can give me is really appreciated. Thank you!
Here is what my sweater looks like:

top- (working edge)
VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV

VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV

VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV (armhole bindoff here- switch to stockinette)

VVVVVVVVVVVVV (body - all knits on circulars)
VVVVVVVVVVVVv
VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV
VVVVVVVVVVVVV

#2

I’ve heard of gauge changing when you go from knitting in the round to knitting straight, but every third row? That is odd. I can’t think of anything to help, just to agree that it’s odd.

#3

You may have “Rowing Out”. I struggle with the same thing. One tip I read was to switch to a smaller needle when purling…easy to do on interchangelables…not so much on regular circular.