seeing the same behavior with iPhone 6s and iPad Air on Collector 18.0.1
this map was created using a hosted Feature Layer in AGO and works like a charm when in online mode. when we download the map to a device, Collector crashes whenever we try to add, edit, or view a record from a related table
all the related tables were added to the map at the same time when the feature layer was added (so the URLs all match up)
would love to be able to report this as fixed - any word from Esri?
has anyone found a workaround?