Weird steering problem - wheel changes position but does not affect allignment?

[Corellian Corvette]

OK steering experts, here's a problem I've never encountered before.

68 Charger, Power Steering, Firm Feel Stage 2 box, Front disc brakes.

The car was aligned and drives really straight. No problems there. When the car was aligned the steering wheel was centered and everything was normal.

The other day I realized that the steering wheel was now tilting about 15 deg off center to the left. WTF? The alignment is still fine, car still drives straight, but the steering wheel is off.

Sometimes the steering wheel comes back to center. I found that sometimes, if I turn the wheel hard to the right, with the car off, it will "re-center" the steering wheel. Then, a little while later, the steering wheel will be back crooked to the left.

What in the HECK is causing this to happen? For the life of me, I cannot figure out how the steering wheel can change position but never affect the alignment. The only thing I could think of is that the steering coupling is loose on the steering box, but if that were the case I would hear some noise or the wheel would change position all over the place.

Anyone ever had this happen to them?

[elacruze]

Telephone Diagnosis!

1. loose steering box on K-member, or cracked mount
2. UCA eccentrics moving

[HPP]

...or the valve block on the top of the steering box is just ever so slightly loose and has been tapped off center to the left.

[elacruze]

...or the valve block on the top of the steering box is just ever so slightly loose and has been tapped off center to the left.

[375instroke]

Jack the front tires off the ground, turn the steering wheel all the way to the left or right against the lock, then force it a bit.  Then, by pushing on the tire itself, turn the suspension in the other direction against the lock.  Now have someone force the steering wheel in that direction against the steering stop while you look at the steering system for movement.

[Corellian Corvette]

I put a marker on the steering box and the column to see if it was moving. I can confirm it's not slipping.

I did notice that the UCA eccentric bolts were not super tight. There was at least 3/4 to a full turn left on all four bolts. I'm hopeful (fingers crossed) that was the problem. Will drive around tomorrow to see. If that doesn't work, I'll do a more thorough inspection.