I Purchased a second hand machine and have replaced a few parts already, but have just found out that the middle (double) button is not returning properly when cancelled. It comes back out only half way and very slowly, I have to manually bring it out the rest of the way. Has anyone else experienced this problem? I did replace a part on the underside of the carriage at the front which has two white plastic pieces on each end, while doing this I removed a screw which is directly under the middle button and am wondering if there is a spring inside which is now no longer connected to anything, Is this all too techie ? Any advice will be appreciated.