When the unitegallery.js script (https://unitegallery.net/) is present on a page, Pinegrow’s text editor stops functioning normally. The left and right arrow keys which allow you to move through the text character-by-character stop working, and cause the cursor to jump to the beginning or end of the text block. Disabling javascript or removing the unitegallery.js script from the page allows PG to function normally.
It must be the gallery capturing the keystrokes. Nothing we can do about it. Disable JS when editing the text.