If one of your scenes, when you open it, is not displayed properly (white, or all elements are floating on top of each other),
then this is usually caused by a device being removed.
As such the block is missing and we cannot display properly your blocks.
If you do not want to redo your entire scene, you can manually repair the xml file.
All your scenes are saved in:
If for instance you removed zwave device numer 5 (zwave-5), then you need to replace it with either a similar device (eg: zwave-4) or remove the xml blocks concerning this device.
After saving the fixed xml, it will be displayed properly as well.