I think this feature with a following "bug" has been introduced in SU2018.
Recently (sometime in a past year) it has been taken a while for me, to recognize what magic is going on with the rectangle tool, if I draw the rectangle precisely by typing a length value then width value.
There were no problem with mouse, and I have been aware of the new feature with Ctrl key.
You know what happens: Each odd rectangle is drawn from the center and every even is drawn from the corner.
Explanation:
I have a different keyboard and language settings than English, so I have to use a comma , to indicate the decimal place (decimal separator) and a semi-colon; to separate the dimensions (list separator). To get the semi colon first I have to push AltGr (or right Alt key) and the key above it.
Since the AltGr ≈ Ctrl+Alt , you see, it is initiating the Ctrlkey too. … to toggle between center and corner-based drawing. 
Unfortunately, I still tend to forget about it …