I have encounter a problem with adding images to gallery using VisualEditor. The software was not behaving like that in the past. If I add manually the image name, VE ends with no result. Steps to reproduce are in this video, the problem starts to be evident at 1.24. https://www.youtube.com/watch?v=2FBs73T68GI
The only way, how to bypass this problem is delete preload string in search box and paste mine. Otherwise it ends like described before. Tested in both FF and Chrome, loged in, loggout.
I would remove this behaviour, because it eats time of an editor. If adding one gallery, its just a few seconds, but last time, we were doing this for hundreds of articles and than the time rise up.