Steering locked - 2008 ForTwo

The steering on one of my two 2008 ForTwos, my Pure (81K miles) locked up this morning, engine running or not. Car definitely has power steering, historically was easy to steer, but the steering wheel felt like it was mechanically locked in place.

Running car shifted into forward & reverse, moved straight forward & backward. The steering wheel moved just a few degrees, maybe the right amount of play in a steering coupler.

26 degrees now, but the Smart has seen much colder in 12 Chicagoland winters.

I’ve read in our other threads that we have no anti-theft-purposed mechanical steering lock, & that power steering is electric-assist, & there can be no steering fluid issues.

The few posts I’ve found of locked steering behavior like mine invariably end with no resolutions posted - the OP doesn’t describe the failure mechanism or the resolution / fix.

Decided to warm the car interior on high heat for 30 minutes & then recheck. Steering was still locked. Looking under the dash, I tugged on the wheel, saw that slight steering wheel movement caused the steering shaft to rotate slightly where it disappeared through the firewall, looked outside at the tires to see any tire movement, NONE…. Another steering wheel tug…. It rotated freely.

No click, no bang, no audible hint anything had changed…. but the steering wheel was free.

Helluva thing, the steering locking up. It was about 9:45a this morning I noticed it locked. The lock cleared a few minutes ago, about 12:30p.

Not looking for speculation on the many potential locked-steering causes. Anyone here KNOW what ultimately caused any of our steering locked behaviors & what the fix entailed?