Still not a lover of steer by wire. If for some reason the mechanical clutch did not activate on an electrical failure.

There may be three elecrical systems. The system responding with the agreeing two. Say a power feed wire burnt to them they would all be deactivated. This incidentally is only one backup system if right. Besides the electrical clutch.

Total loss of steering was not that uncommon in the twenties cars. It is or can be far worse than the loss of brakes. Could also be failure prone with age.

I think rather than an alignment shop. Perhaps rotate tires front to back and see if symptom remains.

Sounds like a system that can go out of normal. A simple off value sensor for example. Two computors would agree with the issue and perhaps pull in one direction. Actually all three perhaps would agree although that is not required.

Quality road feeling and tracking have existed in the past. My 1950 mercury had it in spades. Even as the crown of the road changed no steering correction was required. Also for the time that car had really effective non power larger drum brakes.

That car just seemed to have well though out design in those areas. Another car that I personally liked the steering feel was an early mercedes 220 fintail. Although with the wrong tire choice it would seriously understeer when pressed so you had to keep that in mind. I finally found a brand of tires that seemed to reduce the issue.

I would periodically check that the electrical clutch was remaining functional as well in any steer by wire car. You might also just phone a buick dealer to find out if it is an issue they see often and the probable cause.