Trouble with disappearing text

Anyone having a problem with disappearing text? I'm not sure when it disappears or what causes it. 

It doesn't disappear completely, I can select it, copy it and then replace the original text. 

I can't select it and bring it to the front as that doesn't change anything.

I can't see any reason for it, its a common procedure for me, nothing different. To me...it seems like a glitch. A program issue? 

I've not seen it happen with any other graphic elements. Just text. All look of text were typed on a curve...I don't know if that's an important factor but it is a common one.