The only times I've ever found a FW to be temperamental was when the bobbin assembly had been removed to clean and had not been reassembled correctly, had thread wrapped around the bobbin assembly, the needle inserted with the flat to the back rather that to the left or were threaded left to right rather than right to left. Otherwise they are so simple and reliable. They are so lightweight they are my go to travel machine when a straight stitch machine is required. If I need zig-zag or buttonholes, my Brother NX-400 is the machine I grab.