Enabling the Preserve During Load preferences can lead to regions being shifted by 0.5 pixel in both X and Y directions.
CIAO users should not enable either of the following options in their preferences:
Menus and Buttons → File → Menu → Preserve During Load → Pan Menus and Buttons → File → Menu → Preserve During Load → Region
Due to the way CIAO starts ds9, having these preferences enabled leads to a half-pixel shift in regions. This shift accumulates if the region file is saved and re-loaded.