Report your bugs here - if someone else has already mentioned the same bug, just add on to their post with as much info as possible to make the hunting easier.
I don't see any difference between a custom text field and a custom field in Pedia 5.0.0. Both are one-line only and both remember input in Auto-Fill. I would expect the custom text field to be a mult-line free text entry box that doesn't use Auto-Fill. Like the Summary pre-defined field. Looks like we may have a bug here.
Thanks for pointing that out. Bug will be fixed for the next version release. If you want the fix right now, download the betas from the following links: DVDpedia, Bookpedia, CDpedia, Gamepedia