Hi,
current sql developer version is: 17.4.0.355
when I get an error, first error message is in Turkish and rest of it is in English (which I was getting all messages in English)
here is my nls parameters:

"hiç veri bulunamadı" means "no data found" in Turkish.
when I checked NLS_SESSION_PARAMETERS for NLS_LANGUAGE, it is Turkish (even if it is not set in the properties):

with same parameters, it is in English in 17.3:

when I checked nls_session_parameters in this version 17.3:

this is not something big of course but really disturbing, even if it is in my own language(Turkish) I don't understand the error messages sometimes
thanks.