I am currently working on a machine with a lot of noice on the limit switch cables and the swicthes are trigered once every few seconds. I have used the search function on the forum and came up with the solution that you need to put a capacitor over the input and gnd with 0.1uF capacity.
The question i have is is this capacitor a DC Elco capacitor or a AC capacitor. In my collegue years we have looked at a schematic of a power supply and there i think the elco was for buffering and the normal cap for filtering but i am not shure anymore.