Check to make sure that the ends of some of the letters are not overlapping and creating an overlapping sketch. Usually look at the letters beside any A. I've had to increase the spacing slightly on some text sketches to eliminate the overlap
It's most likely one or more of the individual font characters splines/ lines overlapping or not meeting end-to-end per the tolerance or relative tolerance the model is using.. Test this by trying the most likely or complex character and see which one fails? You could always change the font and see if that works? Or if you absolutely have to have that font, you can copy edge the failing character and click on the corners to force then ends to meet, then break the edge relationship and delete the bloody sketch. This way is suggested if you want to reduce or eliminate the chance of having your model rebuild,... rebuild,.... rebuild,... for ever and ever and ever..... you know what I mean!?