GENERATED ALWAYS AS - Not Consistent with MD5

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/ddl-generated-columns.html
Description:

In my table definition - my Id Column is defined as ```Id TEXT PRIMARY KEY
GENERATED ALWAYS AS (MD5(date_part('epoch', Inv_Date)::TEXT || TerminalId ||
GradeId || Ownership_Code)) STORED,```

But the value generated is not consistent upon insertion.
To confirm we checked by generating MD5 on SELECT and comparing the Id,
they're two completely different values.