It wobbles, bends or looks like jelly
Subspace Warp stabilises by bending small regions of the frame differently, and on shots with strong depth, close objects or plain surfaces that bending becomes visible. Adobe’s own advice is to choose a simpler Method: Position, Scale, Rotation first, Position if that still distorts. Perspective can add keystoning, where the frame’s edges seem to tilt towards you and away.
Ripples from the camera’s sensor
Fast shake on a rolling-shutter sensor makes each frame slightly bent, and stabilising can expose it as a ripple. Set Rolling Shutter Ripple to Enhanced Reduction. If you only need to straighten leaning verticals without stabilising, After Effects and Premiere both have a separate Rolling Shutter Repair effect; rolling shutter, explained shows what causes it.
It crops too much
- Lower Crop Less ↔ Smooth More: the quickest fix, and it needs no new stabilising pass.
- Lower Smoothness, so the virtual camera stays closer to the real one.
- Choose Stabilize, Synthesize Edges to fill the gaps with picture from earlier and later frames. Adobe warns of artefacts when something moves at the edge of the frame.
- In After Effects, a red banner suggesting Stabilize Only means the crop has become extreme; take it as a sign the shot may be too shaky for a clean result.
For the general trade-off between steadiness and crop, and ways to keep the whole frame, see stabilising without cropping.
It follows a person instead of the background
Warp Stabilizer tracks points all over the frame, so someone large walking through it can drag the result along. Try Detailed Analysis, trim the clip around the moment, or in After Effects delete the track points on the subject so the effect stabilises again without them.