How to stop the fabric puckering

Stitch length is too long for material - Decrease stitch length.

Needle point is blunt - Replace needle or correct size and type.

Incorrect thread tension - Reset thread tension.

Presser foot wrong type - Check you have the correct presser foot on machine.

Fabric is too sheer or soft - Use material backing or tissue paper.

Using two different sizes or kinds of thread - Upper thread and bobbin thread should be the same size and type.