My model 50 is only softening water 50% of the time.

I completely emptied the salt tank and cleaned it out thoroughly. There was a lot
of salt debris under the plastic shelf that I removed. I then replaced the plastic
table and put just enough salt on top so I could see what happens when the unit
regenerates.

The unit regenerates on it's own about every three days. When regeneration starts,
water is sucked out of the salt tank and then maybe 10 minutes later water is
returned to the tank.

Operation seems normal, but water is only soft when the Remote tank is in service.
I verified this with Hach Test strips and when the Main is in service, no soft water.
When the Remote is in service I get soft water.

Can the 2 tanks be swapped so that the Main becomes the remote and the Remote becomes
the main. This should prove whether or not the resin in the Main tank is bad.
Am I correct in this assumption.

I have been tracking the tank in service for over a month and results are very
consistent. Remote in service - soft water. Main in service - no soft water?

How easy is it to swap the tanks and does anyone have a diagram on how to do this?

Suggestions?

Thanks