Well, basically the chiselled shelf is charging the redstone comparator, even without books. The only way to remove the charge is to break and replace the block, but after 1 book is placed, The bug occurs again. It's old, but it's never been fixed. That's why I'm reporting. Attached is the video of the bug in action. Again: The bug is an invisible load that should not occur on the chiselled shelf, and that prevents dozens of systems.