Fix for "Please enter a valid input" due to duplicate IDs

Look at app model to see if there are form elements with duplicate IDs. Then manually change one ID and save the app:

EG: APP_MODEL.attributes.data[0].idx "0a29c11b_1542174882276" APP_MODEL.attributes.data[0].idx = "0a29c11b_1542174882277"

then Save.

Also ask the Wobbly how this happened so we can fix properly!