Windows limitation in PCB window in Altium
According to the Altium 20.0 designer documetation


  The board can range in size from the miniscule, right up to 100x100 inches, using design objects down to 0.001mil in size.


100 inch = 2540 mm

Maybe your board runs from to + 2360 mm, so you hit the max board dimensions at -180 mm?