I've not heard cèithir pronounced like that before.
Just had a listen, it sounds very normal to me.
the final 'r' sounding like a 'th'? Because that's the recording I got. I'm not sure if they have only one recording per phrase or not.
Ah, cool. Ceithir has a thin r at the end which is pronounced somewhere between and r and a th sound. The degree of th depends on the speaker.
Might be regional.
Ceithir, with no ` by the way.
It's pronounced as coìg for me. Possibly a bug?