This is on a world hosted in Realms. In the nether, I put up a sign and create text. I complete the sign and the text is on the sign. I take a portal back to normal space. I return through the portal to the nether and the sign is blank. 

I need to leave the location and return for the text to disappear. It does not happen to all sign but most of the time, the text disappears. 

This seems to have been introduced sometime recently as I have many signs in place in the nether.