If the presser foot twists or leans off to the side it will affect your stitches by twisting the fabric as it feeds it.
If the foot is so wobbly that it won't sew straight, it should be replaced.
Here is a quick two step way to check the alignment of the presser foot:
A: remove the needle and turn the hand wheel till the feed dogs are below the needle plate. Lower the foot while looking at both sides of the foot and the feed dogs at the same time. If the side of the foot are not lined up, you'll be able to see it.
B: put some fabric in the machine and slowly run it while you watch the fabric. Does it feed straight or does it twist around and feed at an angle?
If the foot is straight with the feed dogs and the material feeds straight, no problem.
If the foot is at an angle with the feed dogs and / or it feeds the fabric crooked then you need to try a new foot/ankle assembly or a solid foot. {NOTE: The new solid feed as sold by just about everyone are thicker on the bottom than factory Singer solid metal feet. You will loose some clearance between the foot and needle plate with some of them.}
If a new foot does not correct a crooked feeding problem go back to "A" and check the alignment again.
If it's crooked, the presser foot shaft might need adjusting.
Joe