See this page:
https://helpx.adobe.com/mt/premiere-pro/using/motion-position-scale-rotate-clip.html
And search on that page for "Modifier keys." You may want to search for "Anchor Point" and read all the entries, but Modifier keys gets you to the nitty gritty for your question.
Right before the modifier key entry, it says 'When you drag the anchor point in the Program Monitor, the anchor point gets relocated in the Program Monitor while the frame remains still. It is achieved by simultaneously updating both the Anchor Point and Position parameters."
Then it says "To update only the Anchor Point parameter and not the Position parameter, press the Alt (Windows) or Option (macOs) key and move the cursor over the anchor point, the cursor changes to [see the help page for the symbol]. Then, drag the anchor point in the Program Monitor. It drags the frame while the anchor point stays in place."
The point being that these are intentional actions. If the anchor points moves, either the frame must move or the position (which is relative to the anchor point) must adjust.
Stan