Here are a couple of tips which I hope you will find useful:

You do need to make sure that when you have two pieces of fabric being sewn together that they start and top together – don’t assume that the machine will do that for you because the way the machine works is the top fabric is being pushed towards you and the bottom fabric being pulled away from you;  this ‘drag’ varies on the machine and on the fabrics you are using and a little with the foot you are using.   So always hold onto the fabric with a pin or with your hands until you have sewn right to the bottom and if you are using a thread catcher, this will encourage you to do this.

If you are sewing a triangle onto a square so that you have a bias seam,, do still hold onto the pieces but try not to hang onto them so that they distort – the machine will sew quite happily in a straight line if you let it!!!

We have a workshop on Precision Piecing that might help

and don’t forget that you need to achieve that 1/4″ not just assume – again there is a workshop to help you.