Sub-tables / Nested tables not available for join any more

Wappler Version : 5.1.1
Operating System : W10
Server Model: NodeJS
Database Type: PostgreSQL

Expected behavior

When adding a table to join, all tables in the DB should be shown.

Actual behavior

Randomly, if a table has been identified as a subtable using foreign key relation, it stops showing up in the list of table for join.

How to reproduce

No set way to reproduce this. For a table in my DB, I have multiple subtables showing up like that due to foreign keys. But after selecting the main table, one of the subtables does not show up in the list of table to select for a join. I have no option but to add that as a sub table and use index [0] in binding - where a simple join should have worked.