That thing you're doing on the left side? Do it on the right side
My guess, without seeing you, is you're probably tracking the paddle in a nice straight line and holding the paddle nice and vertical on your left side (ie not following the board outline) and on your right side you're either sweeping the paddle around a bit or not holding it vertical (or both). This'll happen if you're right handed. You might also be weighting a rail a little when paddling on your right side.
See if you can get someone to video your stroke from a few angles, you might be able to pick what you're doing. Even better - book a session with a good instructor/coach who can check you out and give you some corrections.
If you can't do either of those, slow down observe what you're doing on the good side - and incorporate some focused drills in your sessions - focus in keeping the paddle vertical and tracking the paddle straight on your weak side. There are a few good stroke technique drill vids on youtube.