Dress in knit

I'm pretty new to knits (hopscotch shirt several times), and am trying to do the knit version of the playtime dress. I'm having difficulty attaching the bodice and dress. The layers are slipping and bunching and catching in the seam. I'm using a lightning stretch stitch (that is a nightmare to unpick), and my walking foot. I also had difficulty with the button holes even though I used interfacing as instructed. I have done this pattern easily with woven. Any tips? Is my knit too thick (it's a Lizzy House Andover knit with 5% Lycra)?