Hi Ben, if you have database access my suggestion would be to work through that database step manually.
https://github.com/ILIAS-eLearning/ILIAS/blob/release_5-2/setup/sql/dbupdate_04.php#L15276-L15327
I'd first check to see what's in il_dcl_field_prop_b AND il_dcl_field_prop_s_b(its sequence table)
SELECT * FROM il_dcl_field_prop_b;
SELECT * FROM il_dcl_field_prop_s_b;
As well do a
show create table il_dcl_field_prop
to see if the table structure matches what that update step says.
Feel free to share what you find here and we can go from there.