TRIANGLES AND ! SIGNS EVERY WHERE

Yes this also happened to me after updating desktop editor, nearly had kittens!!! I restarted the editor and then all was well with the world. Think it was just a glitch, perhaps file references to entities issue? Seems like the editor knew there was supposed to be an entity - the presence of warning triangles in place of where entities should have been would suggest this - but editor couldn’t find the location.  Hope you managed to get your world back ok!