I had the same problem. Some workaround here: write to_nchar('String') instead of 'String'. But this, of course, cannot be considered as conclusive solution to this problem. This is a bug in this version of SQL Developer.
try it on instance with NLS_CHARACTERSET = CL8MSWIN1251,encounter the same issue,
if the NLS_CHARACTERSET = WE8MSWIN1252, no this issue
you can try other character set
Thank You for response, but infortunately I can't take advice.
I had this issue with NLS_CHARACTERSET = CL8ISO8859P5, not a CL8MSWIN1251.
I can't change database parameters on all instances I use as I am not DBA.
Moreover, it would be wrong, because the data in DB contain national characters that cannot be represented in a character set WE8MSWIN1252.
I think this is not the best idea - to change the encoding of whole database, because there is a bug in the SQL Developer.
Tanks all for workarounds, but it's cannot be used in production database..
And, take in consideration many other bugs, the better way is to wait next release..
Thanks all,Raised NLS bug in system