FYI to other addon developers, it also appears that ZOS has introduced a limit on the maximum size of strings stored in saved variables. If your string is longer than (guessing, not verified) 2048 characters, it will be replaced with something like
Code:
["showTitle"] = true,
["body"] = nil -- invalid string value,
["medium"] = 0,
Unfortunately, because the comma is also commented, if there is another table value on the following line, the it will be missing a preceding comma and the parser will be unable to read your saved variables, and so on the second logout, the entire file will be overwritten with an empty one.