Editable Field Bugs incl. Copying pulldowns

I have been experiencing some weirdness when updating a PDF that I created last year. The PDF contains a range of editable fields including 10 pulldowns for the user to choose from.  These pulldowns contain about 15 choices and each pulldown is the same but with a different name. Last year this was very straightforward to create but when trying to add new options to the pulldowns the PDF has not been liking it.

Previously when creating the duplicate fields I could just click and drag to copy them. Then rename them and continue to repeat the process. However, now when I attempt to do that, it renames the copied pulldown with a sequence # and renames the original with a #. It lets me rename the pulldown but won't remove this sequence # that has been added. I need to keep my original naming as we use a data import script but there doesn't seem a way to remove the automatic naming that acrobat is making.

What was even stranger was once I had finished updating all 10 fields I closed the PDF and when opening it again all of the new fields had disappeared. I went into the prepare form again option and noticed that the new pulldowns were not visible but clickable. In the properties they were all set to visible, when toggled nothing changed. These invisible pulldowns could not be deleted and the layering was all out of whack. When deleting from layers they were still selectable in the PDF but none of the properties were changeable.

I've tried multiple alternatives, like right clicking and creating multiple copies, dumping my preferences but I still get the same issues. Even when I copy fields to a new form and start again I still get the # sequence naming process occurring.

Additionally, I'm getting the occasional crash when working with this PDF too.

I'm not sure if a recent Acrobat update has caused this? I'm using a Mac and everything is updated in CC and OS. If anyone can shed some light on my issue that would be greatly appreciated.

Many thanks,

Steve