Does your machine have a feed rod clutch? I remember seeing a YouTube video of a PM1127 that had a clunking sound while making a cut. There was also a slight hesitation of the carriage during the cut when the clutch slipped intermittently. Unfortunately, I do not remember which video. There are 4 ball bearings, springs and set screws on the right. The left side has 4 radial grooves that capture the ball bearings. If there is a crash or some binding in the feed rod, the clutch will slip making a clunking sound. Also, I believe the clutch can be used in conjunction with the carriage stop.
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