Drivers door acctuator... again 1 year later

[ScottS]

only fitted a brand new door drivers door acctuator last November, been fine up until now and it's doing the same again, not unlocking from the fob most times, rang Audi but they won't do any warrenty on the part as they didn't fit it, I fitted it myself
Will it just be a case of fitting a new one or could the issue be something else like battery voltage?