Turn smart guides off (and possibly any snapping)
It should be fine now
I agree. Having Smart Guides on makes the scale tool appear erratic.
Are you perchance a FreeHand user?
The reason I ask is: In most of the operations depecited in your video, while difficult to see, it appears that you are beginning your drag very near the scale origin (the little crosshair icon that defines the center of transformation). That's what one does in FreeHand. In Illustrator, unintuitive as it is, for greater control, you begin your drag farther from the center of transformation. For proportional uniformity, you ShiftDrag diagonally away from the center of transformation. So...
- Get the Scale Tool. The COT marker by default appears at the center of the selection's bounding box.
- Position your cursor a significant distance away from your object, and in a roughly 45° diagonal direction from the COT marker.
- Mousedown and drag away from the object in a roughly diagonal direction while holding Shift. The Shift will constrain your drag to a strictly 45° multiple, and the object will scale uniformly. The greater distance away from the COT marker you mousedown to begin your drag, the less severe (finicky) will be the scale factor. If your drag direction is closer to horizontal or vertical than 45°, the Shift key will constrain the scaling to either horizontal or vertical, not to uniform.
AI-accustomed users think this intuitive. I don't. I consider it backwards. For one thing, it imposes an unnecessary space limitation when zoomed into what you are scaling.
yup - after watching your video, I'd agree with the above....clik on the outer edge of the bounding box when using the tool, you'll have muh more control over what you're doing....hopefully!
This may or may not be helpful, but I've just about stopped using the scale tool at all.
You can select an object, then in the Transform panel, type the desired size into the width & length fields there. You can lock them to scale proportionately, and you can even type '200%' if you want it twice as big, but don't feel like doing the math.
Note that you can turn on/off Scale Strokes and Effects here in the pop-up menu separate from the app preferences.