Resolve the quirkiness of statue traps - they are a silent trap on which a real statue potentially containing spellbooks can generate, which you can teleport off the trap to smash for its spellbooks (indicating it’s a true statue) and do not show up with telepathy or monster detection (indicating it’s a true statue), but reveal themselves as “You find a foo posing as a statue” (indicating it’s been a living monster all along). There are two basic options:

1. Statue traps are posing monsters: Remove statue traps as a floor trap. In their place, put real but non-moving monsters that appear as statues of themselves, using the monster appearance system used by mimics. This means that you can see the monsters with telepathy and monster detection and you can’t exploit it to get spellbooks.
2. Statue traps magically animate a statue when someone moves onto their space: Searching for traps may still reveal statue traps, but it does not activate the monster. This implementation might also actually remove statue traps as a floor trap, and instead use the otrapped field on the statue object, so relocating the statue doesn’t affect its trapped status. Trap detection should still show trapped statues.