No, this error occured yesterday after adding into theme language po file ( " turkey " > " Türkiye " translation.
Accidently I did not made backup before uploading edited po. file,
Correcting this problem now cost for me 24 hours, I am still busy and I almost completed correcting of this error;
How I solved ? ;
Normaly English language was disabled for admin and website ( Only Turkish was ), now I am enabled English Language for website and for admin panel, too.
Each category / subcategory I have clicked to edit and selected " Turkish " language and saved.
After this transaction "_1" removed behind of URLs of categories / subcategories automatically.