Problem with Fill & Sign

I'm using the latest Acrobat version on a 2019 iMac.

I'm filling a form sent by an institution, and everything has been fine until I reached the 'signature' dialog box.

After adding the digital version of my signature, I can't escape the 'Signature' function and get back to the 'Fill' function to finish entering other information.

Whenever I click on 'Fill & Sign' under 'All Tools' now, it takes me to the 'Request E-signatures' side bar and a pop-up appears saying 'The author of this form has specified the fields you can fill. Click on any field to start filling form.' 

But all the previously-accessible fields are now unselectable.

I also can't select the digital signature I just added.

Am i missing some easy way to escape the 'E-sign' area?

Or has the document automatically assumed that I've finished because I added the signature, and locked me out?

Any help appreciated.