In develop mode in LRC 10.4 after selecting multiple images and trying to sync the settings a dialog box used to appear where I could select which settings would get synced. The box does not appear any longer. I tried control tab and it shows a second window open, but the background and text are missing. You cannot go any further until you close this invisible dialog box and then sync will occur. I tried closing lightroom and re-booting the pc with no effect on the issue.