Internal error

I am receiving an internal error when uploading pdf files to the Files app via safari and chrome. The specifics of the error: Couldn’t communicate with a helper application

I have tried restoring iPhone and reinstalling iOS. This is rectified another error (could not acquire startup assertion) however the above mentioned error remains.

Is a further restore likely to rectify the helper application error? What is the helper application in this case? Is it the Files app?