Thanks for the tip. I haven't looked much at the ghosts' logic because the Animated Picture extension (Custom Object) doesn't support semi-transparency. Meaning, I can't reproduce the ghostly flickering. If it's a bug, I'll fix it.
Edit: Talps, you were right. Ghost objects 4 and 7 had the same programming that broke the Spider. It's easy to fix when you know what's causing it. I don't think it's off topic to ask if anyone knows of any other glitches in Knytt Stories. I know about the umbrella getting stuck on if it's shifted off while in use. I also know that certain objects will get sucked through the contact layer due to slopes. (Put the purple lizard, 3:19, between two 45 degree slopes if you don't know what I mean.) Oh and, it's not really a glitch but creatures walking off ledges looks odd.