To add to this, I am finding that, with SAS turned off, the Mk1-3 Gumball will start to gain lift during reentry.
To reproduce,
1. Launch a rocket high enough to clear the atmosphere
2. Decouple so the only remaining part is the Mk1-3 Gumball
3. Disable SAS
4. Allow the Gumball to fall back towards Kerbin
The Gumball, after either gaining enough velocity or perhaps hitting thick enough atmosphere, will begin to tilt and accelerate tangentially to Kerbin (that is, parallel to the ground), and after a few moments, the acceleration vector will start to point back towards space.
