When creating a new metadata element (datatype "text"), it's possible to set the "min/max number of characters" field empty (see screenshot).
(Default is min=0, max=65535)
In that case, the following error message always appears when trying to populate that metadata field later on (see screenshot):
"Value must be no more than characters long"
Although I agree that I shouldn't have set the min/max values to empty, but if that is not a legal option, it would be good to have a warning when saving the metadata element
Firefox 56.0 (Ubuntu 16.04.3)