Sculk sensor actived by nothing?

i cant get videos because my pc is so bad when a video is being ruecordedd so i only have screenshots but i dunno

 

how to reproduce:

mess around with a sculk sensor

there were no entities in the area. there was a warden, it doesn't activate sensors though, doMobSpawning was disabled, and in spectator there were no mobs. to confirm there were no mobs, i did /kill @e[type=!player,type=!warden] and it turned no results.