In Sitecore 8.x (and possibly 9.x but can’t confirm) if you get a red bar at the top of the page when trying to save in Experience Editor with an error message that looks something like this:
An error occurred. [Log message: After parsing a value an unexpected character was encountered: t. Path ‘scFieldValues.fld_504A9E8795B1458CA24E1117F3AED60A_FBAB79F728054AB9B86996CFC31F061D_en_2_f13e115eea254229a2d5439b325848e3_5220’, line 1, position 3850.]
This likely means that one of the fields on the page or a component data source contains encoded html that Sitecore doesn’t like. In my case it was %22 (or double quotes). To find the item that contains the encoded html take the immediate guid after “fld_” in the error message and convert it to a “full” guid. In this case:
Pop it into the search bar in the bottom right of the taskbar in Sitecore’s desktop interface and the item will appear. Then locate the offending encoded html and fix as necessary.