SELECT COMMENTS
FROM SYS.USERTABCOMMENTS
WHERE UPPER(TABLE_NAME) = UPPER('TBL1');

Result: 'some comment'

COMMENT ON TABLE TBL1 IS 'next comment';

SELECT COMMENTS
FROM SYS.USERTABCOMMENTS
WHERE UPPER(TABLE_NAME) = UPPER('TBL1');

Result: 'next comment'.

When I open table TBL1 for edit, comment field contains previous comment ('some comment').
PS: When i reconnect to DB comment not change

Version dbForge for Oracle : 3.1.243 Pro