During a job today, the S-Tube of my pump got stuck on every other stroke.  I have to manually switching the "test" switch every other stroke for the S-Tube to strike.  I have 2 prox switches at the water box and 1 at the other end.  I used a little force to push and pull  all three and after awhile the pump work fine again.   I'm not sure which one is causing the problem.  There were no movement when I tried to push and pull the prox switches, but I noticed one of the harness is kinda loose compare to the other two. Please see picture of the yellow harness.  If the harness is good, how can I tell which prox switch is bad by just looking  at where the S-Tube is stuck?

does the main pump pressure up before the s tube shifts.

on prox switches the bad barrel with have the switch on the opposite barrel.

there is four check valves. three pointed down are all the same. the odd one is horizontal at the wash box. the mud cups blew and the fines got sucked up in the fitting. let me tell you that seventy buck part raised hell with my pump till it got fixed