I created a custom field that I no longer require, but when I go to delete it, it does not disappear. Something seems to be blocking it. I have the latest version of Metabox AIO installed (3.7.1). It is running alongside the latest version of EtchWP (1.4.19) and ACSS (v4.0.0-rc-3).
Can you please explain more about this step when I go to delete it, it does not disappear? Where do you delete it? Have you tried to find the field name in the database, table wp_postmeta?
Deleting a field in a field group won't delete the data in the database. You can go to Meta Box > Tools > Remove custom field data section to find and delete the field data in the database.