On my Ender 3 v2 printer I recently and consistently get some knocking. This happens in only two scenarios.
First, it now occurs all the time when printing the initial test strip gets near the top (high Y value), and knocks several times.
Secondly, it occurs if the model (sliced with Cura) has a high Y value (eg: if the model occupies most of the bed). (If there is room and I move the model - in Cura - closer to the front there is no knocking.) On the first 10 (or so) layers the printer sometimes knocks when a high Y value is reached and the entire model is thereafter shifted to the front by a few millimeters.
There is a third scenario. At the end of a print the print head is in the middle of the bed and moves up 20 mm then travels directly to the top left corner. At this corner there are 4 or 5 "knocks" (and the nozzle is 20 mm above the bed).
Any suggestions to diagnose/fix this problem will be much appreciated.