Missing Mandatory fields error while they are provided

in one of my doctype, mandatory fields are provided but still the system showing that those mandatory fields are required, while i try to save.
what’s the issue?

always Or once
Or once
If it is only once you have to refresh the page
else

or

The error message also shows missing mandatory fields along with Doctype Name .
Check it again. You can also check mandatory fields in your created Doctype .
Setup >> Customize Form