Hi Admin
Here is another glitch that i found by mistake
Create a new string field,,,
Try to give the field a name that breaks standards such as "300test" (see the first field in the attached picture)
Save the field
The builder correctly identifies that the field name is not valid
The builder marks the field name with a red border (see the second field in attached picture)
when the field looses focus the field label is returned to the default "My String" and the field name is blank (see the third field in the attached picture)

from here
there is no error notice indicating the field name "300test" breaks standards
I noticed after the field looses focus the save icon is missing (third field in the attcached picture)
if you provide a valid field name the save button does not become visible (forth field in attached picture)

NB: Sorry attached picture but it does not seem to have been saved..

The Workaround
Drop the field into the trash bin and recreate the field with a valid field name
or refresh the page

BTB300

Fixed, now the save icon does not disapear anymore, but there is no validation message indeed. For the moment I leave it like that.