Imported image doesn't update
Import a png image (mine also had an alpha channel - don't know if this is important).
Place it in a comp.
Go to your image editor of choice, alter the image and save it.
Back in Hitfilm, in the Media panel, right click the image and hit 'reload'.
The image updates in the Media panel, but NOT in the viewer window. Deleting the layer and re-adding the image doesn't help. The only way I've found to get around this is to close Hitfilm and restart.