After converting some phpBB 3.0.x board, I've face a problem with TrashBin. I've all the SQL codes for converting TrashBin to 3.1 SoftDelete System, BUT the sql couldn't be runned, because the lack of one column from TrashBin that was deleted by the installer.
And I've found that the post_deleted_time column was deleted because on soft_delete_mod_convert.php file on v310 migration folder, we have a wrong code that is giving false when it should give true after checking the existence of one column "post_deleted" that will means SoftDeletedMOD was installed. But since when that MOD is installed it gives false and nothing is done, and when its not installed, it will run, and therefore, when having Trashbin that have 1 column with the same name as SoftDeleteMOD (post_deleted_time) it will do some operations to the tables and delete that column. And the boards with trash bin gets all f*** up x'D aka we lose all the data from the mod and we're unable to convert it sucessfully to 3.1 system.
More reading here: https://www.phpbb.com/community/viewtopic.php?f=556&t=2439961
TL;DR: The installer run a migration file just when SoftDelete is not installed, but in fact it should only run it when that mod IS installed. And therefor, it dont convert SoftDelete, but will badly convert TrashBin (when it shouldnt convert Trashbin at all)