Unable to update v2 webhook URL

I currently have a functioning v2 webhook which is setup on a folder shared with me. It is configured to call the web hook on "File Uploaded", which is does.

I am trying to change the URL, but I get the error:

"An unknown error has occurred. Please try again."

When I try and recreate the webhook, I get the error:

"A webhook could not be created to trigger on the file or folder you have selected. You can only select content that lives in the service account associated with this application."

It looks like I was previously able to create this action on a folder that was shared with me, but this is no longer allowed? I'm not sure how to replicate the current behaviour I have - web hook called when a file in the shared folder is updated.

Any help appreciated!