When wandering traders attempt to spawn near a village bell, they appear to start their search for a spawnable block at Y = 0 instead of near the bell’s Y level.

Steps to reproduce

1. Load MCPE-151591 Trader Test.mcworld. This world consists of a series of empty 64 x 64 platforms from Y -60 to Y 319. These platforms can be refreshed by pressing the button at 126, -59, 1. There are also command blocks that mark wandering trader spawns with glowstone columns that stretch from the spawn spot to world height and then kill all entities except villagers. When you first load the world, you will be in a small village with a bell in the center of the Y 73 platform.
2. Use the world as it is already set, or kill the villager, reset the platforms, and place a bell, bed, and villager at the center of any of the other platforms.
3. Stand by the bell for a couple of hours.

Expected results

The wandering trader spawns near the bell, since it is the gathering place of a loaded village. It should spawn on the same platform or maybe the one immediately above or below.

Observed results

The wandering trader spawns near the bell horizontally, but near Y = 0 vertically. For example, using the world with the village already set at Y 73, I found that 3 successive traders spawned within 1 block horizontal of the bell, but at Y 1. Using a village at Y 100, the first two traders spawned at the same X, Z, 1 block from the bell horizontally, but at Y 1 and Y -3.

This issue has been on the game for a very long time. I have various player-made villages with a bell on the overworld surface, and Wandering Traders seem to always spawn in the caves underground, below that bell. It gets much worse in 1.18, as they can spawn very deep underground, over 64+ blocks below that bell. It consistently spawns on that spot, never on the surface of my village.

As Wandering Traders are killed underground, persistent Trader Llamas and Zombies carrying leads will accumulate below your base, which will cause lag at 100+ mobs. (See MCPE-102302 and MCPE-125111)

There are various complaints of players unable to find Wandering Traders around their base, and this bug could be the reason. If they always spawn deep underground, players won't notice.

Please force Wandering Traders to spawn close to the bell. It seems like the Y-range spawn can get ridiculously far from the bell. I'm not sure why the Wandering Traders aren't spawning close to the bell, it could be because there are some decorations and clutter around that bell. I've tried giving the trader more room to spawn near that bell, but it doesn't work.