Can't remove tags containing special characters

Hi guys,

I added some special characters (like š,č (regular characters in Slovak language) etc.) into tags and now, they are not showing properly. I can't even remove or rename these tags because I am getting error messages that you can see in the attachments.

I tried to change supported language to ,,sk" in wiki administration but the same errors appeared when removing tags.

My database is set to support utf-8 encoding.

Could you please help how to remove these tags manually or somehow?

Thank you for your help.