it is very unlikely that fitting new gears would have upset the feed unless screws were undone on the bar that connects to the teeth, it is a long time since I saw a 2010 but if I remember the stitch length is electronic, unless you can remember altering any screws on the feed bar you may be looking at an electronic problem, it is possible there may be a loose connection on the board but if you touch the board without the proper earthing strap you may blow the board completely, 2010 were always a difficult machine to work on, I will check on my schematics and get back to you if I can find a simple solution.
drivewithken@blueyonder.co.uk
November 2008