Automated backup to Dropbox failed (ERPnext, Dropbox Integration)

The automatic backup and also the manual backup with Dropbox fails every day with the following error message:

Error message: Traceback (most recent call last): File "apps/frappe/frappe/integrations/doctype/dropbox_settings/dropbox_settings.py", line 76, in take_backup_to_dropbox did_not_upload, error_log = backup_to_dropbox(upload_db_backup) File "apps/frappe/frappe/integrations/doctype/dropbox_settings/dropbox_settings.py", line 135, in backup_to_dropbox upload_file_to_dropbox(filename, "/database", dropbox_client) File "apps/frappe/frappe/integrations/doctype/dropbox_settings/dropbox_settings.py", line 208, in upload_file_to_dropbox create_folder_if_not_exists(folder, dropbox_client) File "apps/frappe/frappe/integrations/doctype/dropbox_settings/dropbox_settings.py", line 246, in create_folder_if_not_exists dropbox_client.files_get_metadata(folder) File "env/lib/python3.7/site-packages/dropbox/base.py", line 1512, in files_get_metadata None, File "env/lib/python3.7/site-packages/dropbox/dropbox_client.py", line 327, in request timeout=timeout) File "env/lib/python3.7/site-packages/dropbox/dropbox_client.py", line 482, in request_json_string_with_retry timeout=timeout) File "env/lib/python3.7/site-packages/dropbox/dropbox_client.py", line 607, in request_json_string raise AuthError(request_id, err) dropbox.exceptions.AuthError: AuthError('4583786f5dbf4e91b50674168c1615f3', AuthError('expired_access_token', None))

The App Access Key and App Secret Key are entered correctly, because if I click on “Allow Dropbox Access” beforehand, the manual backup works. However, the backup fails again the next day. It seems as if the button only creates an access token that is only valid for a short time.

Is there a way to fix the problem?

Used Versions on managed hosting:
ERPNext: v13.50.6 (HEAD)
Frappe Framework: v13.56.4 (HEAD)