jmsbert
I have seen the same issue yesterday, but it seems to be fixed now. 
I assume that this could a) either have been a failure in the editing - as many people are sometimes working at the same time even on the same objects it is difficult to keep the database consistent at all times - or b) it might have been a rendering issue - as updating the tiles may take some time and the tiles of each zoom-level need to be rendered seperately.