"Cleanup using Pathauto" cannot be selected

When configuring a particular file field in a particular contenttype ((path in this instance: https://www.domain.com/admin/structure/types/manage/document/fields/fiel...):
I try to switch off "Cleanup using Pathauto" in the "File (Field) Path settings". Although the radio button is not grayed out I can not uncheck the button. Whereas the 'transliterate' setting can be unchecked.

When I try this out on a file field added to a test content type, using a new file field or the existing field_document field, the radio button is by default not checked but here I am unable to switch it on.

Where is the setting in Pathauto that 'locks' this into its current setting? I am aware that the problem exists on the file field settings page, but I have the impression it is Pathauto which disables (without greying out) the edit.