The Bug:

Trial chambers can override stronghold rooms. This is not a duplicate of MCPE-184013, because this bug report specifically talks about other stronghold rooms in general such as stronghold libraries being overwritten by trial chambers. We are not talking about the end portal room, but rather other rooms of the stronghold.

Steps to Reproduce:

1. Create a world with this seed: 6156517472232198482
2. Go to the following position: 681 -17 -790
3. A stronghold library was found to be partially overwritten by the trial chambers. This is not a small library, because there was ladders in the library leading to just tuff bricks and oak planks at the library ceiling.

Expected Results:

Trial chambers will not be able override stronghold rooms in general.

Observed Results:

Trial chambers are able to override stronghold rooms in general. The reproduction steps will lead you to a stronghold library.

Notes:

This is a possible cause of MCPE-184013.