I'm using the Dynamic Featured Content Gallery plugin, which requires that I add a custom field to each post with the name 'dfcg-image'. I type the name, give it a value and then click add custom field. I then click Update Post and it disappears, as if it was never there. I know this is not a plugin related issue because I've now deleted the plugin, and it's still happening.
If I use the name 'dfca-image' instead (for example), it works fine. As soon as I rename to 'dfcg-image' it disappears again. If I change the theme to classic or default, the same thing happens. I've removed all blank lines from my functions.php file. I really don't know what I've done wrong here.