In version 2.9.9.7 Beta (955095) 64-bit on Windows 10 Home version 1903 O.S. build 18362.900, if text has been selected in the document window, pressing right-cursor causes the highlight on the selected text to shrink – the blue background changes to white and the text changes to black but only in the area below the baseline. The area of the selection from the baseline up remains selected and the cursor is at the end of the selection rather than one space to the right. Pressing right-cursor a second time causes the behavior expected on the first try: the selection is deselected and the cursor moves to the right one space.
After the first right-cursor, if I scroll the page, the highlight disappears (meaning the selected text is deselected). But the cursor is at the end of the deselected text rather than one space to the right.
FWIW, to double-check system behavior, I tried this in Notepad and the behavior was normal…