Please refer to the following video and focus on RA=13:30:00.00. The cursor stays as RA=13:30:00.00 while zooming and the red vertical line should stay at RA=13:30:00.00. However, there is offset at different zoom levels.
In addition, at high zoom level, there seems to be an 1-pixel offset (due to the legacy 0-index/1-index issue?).