When moving the object from javascript using setLeft/setRight (followed by a canvas.renderAll()), the object itself moves but the bounding rectangle stays still.
I wasn't able to find any function to force updating bounding rectangle after a move either, so I believe this is a bug. It happens with a single selected object as well as a group of objects.

Calling setCoords() method fixed the problem. Maybe this should be documented.
old issue, but I'm experiencing the same bug in ver 2.6.0.
after moving objects within a multiple selected with set('left', x), the bounding box doesn't update to the new position
No it doesn't.
You have to call setCoords since you are setting left, you should do it.
Of course, forgot to mention that this is happening even after calling setCoords() on every object in the selection
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Calling setCoords() method fixed the problem. Maybe this should be documented.