@gomerpyle I would start by cleaning all of your limiter switches, make sure there is no build up or anything blocking them (soda cans stuck under the gantry etc.) . Also they are distance sensitive, I believe you are shooting for about the thickness of a nickel between the limiter switch and the metal stop plates. If you can figure out which limiter switch is erroring out, you can swap them around, and see if your problem moves with the limiter switch. Also when removing and replacing the limiter switches make sure to put a bit of dielectric grease in the connection to the sensor to help keep water, dirt, or corrosion out, and if replacing the limiter switch, USE THE PROPRIETARY RECOMMENDED LIMITER SWITCHES! Do not try to use some other brand off
kleenrite etc. as you will cause yourself so many more problems and can have a catastrophic failure.
Make sure to check the limiter switch on your drive wheel in the drivers side of the gantry. The gantry drive wheel has metal "spokes" that count how many pulses it takes to get from one end of your bay to the other (186 pulses from one end to the other etc.). Make sure this drive wheel and corresponding limiter switch are clean and distance between them is within specs. The "end position is not reached" error makes me think that this is where you should start.
Other issues I can think of would be a faulty/shorting wire to the limiter switch, if it has a crack etc. it could be sending errors, if you can figure out which sensor is having the error, follow the wire from end to end to look for nicks/ abrasions.
Did you recently have any service done to the machine? I had a similar error 2 years ago when I replaced the bearings under my gantry and the pulse count from one end of my bay to the other on my drive wheel changed for some inexplicable reason.
Also when does the wash error out? Is it when the full gantry is moving, or when the side brushes come in and start moving around the rear of the car? I.E. which limiter switches to start looking at? If it is when the entire gantry is moving, I would check the drive wheel limiter, and the end stop limiter (located on the back wall side of the gantry on the drivers side.
If it is when the side brushes are moving, check the limiter switches near the side brush motors, and check your gum wheels that the side brushes are moving back and forth on. Try moving your side brushes in and out, and see if one of them hangs up, or the gum wheel moves without the brush moving. If that is the case, look at your gum wheel to see if it is damaged/ separating, clean the rail that they move back and forth on with acetone (we have to do this about every 6 months) and check the tension on the gum wheel to make sure it has enough downward pressure to move the brush and not just spin in place.
Let me know if you need any pictures of the components I'm speaking of, or if you narrow down your issue and I'd be happy to help.