Quick fix: When changing colours, always bring the new yarn up from under the old yarn before working the first stitch. This twist links the two sections and closes the gap.
What you are seeing
A visible gap or hole at the point where two colour sections meet in intarsia or at a row-end colour change.
Why it happens
- Old and new yarn were not twisted at the join
- One yarn pulled too loosely when starting the new colour
- No lock stitch at the join edge
Fix it now
- For existing holes: thread the tail of the new colour onto a tapestry needle and close the gap with a few small stitches on the wrong side.
- Going forward: at every colour change, bring the new colour yarn up from under the old colour before working the first stitch. This twists the two yarns at the join.
- Snug the first stitch of the new colour firmly before continuing.
Prevent it next time
- At every join, always pick up new colour from under the old — this is the twist that locks them together
- Work the first two stitches of the new colour slightly tighter
- In intarsia: twist at every colour boundary, on every row