Problem with menu save function

A problem has occurred with my Appearance/Menu functionality. This week after, having put two or three pages on four of my WP websites and establishing a menu for each of them, I can no longer use the menu function to add more pages. After designating webpage url and titles, I can’t save to the menu. When the “save menu” is clicked, all that appears are empty tabs without any url links included. Even the title is absent from the tab. But it is visible on the internal input slots. There is also a space that reads “original”. But that is an inactive area in the tab input area. When I try to rearrange the menu tabs, a long series of blank tabs begin to show and none can be eliminated except by refreshing the page.