Just ran into another problem in the same vein as one that RobM encountered recently.
Working on some new skin versions. You can make an album with regular thumbnails, but the skin really wants HiDPI, so it puts up a confirm dialog, asking if you want to change the setting. If you say YES, it invokes engine.setHiDPIThumbs(true). This happens in init.bsh.
If the album has never been made before, that works. But if the album was previously made with regular thumbnails, that change doesn't register as something that needs new thumbnail images, and they don't get recreated. It takes a forced remake (which is nasty, because that also reprocesses all the videos). Not even saving, closing, and reopening will cause new thumbnails to be generated.