Teradata Max per Partition with non-adjacent duplicates - duplicates

Question

Okay, this one might be a little tricky, so let me start with a visual.
Here's what the data looks like:
Original Data From Source
I'm trying to simplify it so that it looks like this:
End Result that I'm working towards
The problem is that I have an employee who changed back to a previous manager, so when I try to partition and group the data, those two instances get combined together and I end up with data that looks like this:
Actual Results
In the image above we can see that Manager Tom has a Start and End Date that is within the Start and End date of Manager Bob which is an error. Any suggestions on how to isolate the grouping of a item that gets reintroduced at a later time? This would be determined by Start Date and Rank over Partition I believe, but I can't seem to get this to work.
Here's the query to build the sample data:
CREATE VOLATILE TABLE VT_AGENT
(
EmpID INT
,Manager VARCHAR(16)
,Director VARCHAR(16)
,Record_Start DATE
,Record_End DATE
) ON COMMIT PRESERVE ROWS;
INSERT INTO vt_agent VALUES(12345678, 'Jill M.', 'Mike B.', '2019-08-21', '2019-09-07');
INSERT INTO vt_agent VALUES(12345678, 'Jill M.', 'Mike B.', '2019-09-07', '2019-09-16');
INSERT INTO vt_agent VALUES(12345678, 'Bob S.', 'Mike B.', '2019-09-16', '2019-10-15');
INSERT INTO vt_agent VALUES(12345678, 'Bob S.', 'Mike B.', '2019-10-15', '2019-11-23');
INSERT INTO vt_agent VALUES(12345678, 'Tom A.', 'Mike B.', '2019-11-23', '2019-12-07');
INSERT INTO vt_agent VALUES(12345678, 'Tom A.', 'Mike B.', '2019-12-07', '2019-12-12');
INSERT INTO vt_agent VALUES(12345678, 'Bob S.', 'Mike B.', '2019-12-12', '2020-01-15');
INSERT INTO vt_agent VALUES(12345678, 'Bob S.', 'Mike B.', '2020-01-15', '9999-12-31');
Select * FROM VT_AGENT

Answer 1

Assuming your last insert had the typos mentioned in the comments, you can make use of Teradata's Period data type (and functions) to make this super simple:
SELECT NORMALIZE
empid,
manager,
directory,
PERIOD(record_start, record_end) as valid_period
FROM VT_AGENT;
What this is doing is constructing a PERIOD column type from the record_start and record_end dates. Then we use the NORMALIZE keyword to compress periods where all other non-period columns are equal across more than one record. The result is a single record with the expanded period. This works only when the periods in those matching records meet (the end of one stops at the start of the next) or overlap (the end of one is after the start of the next).
With the assumed typo corrected, this outputs:
+----------+---------+----------+--------------------------+
| EmpID | Manager | Director | valid_period |
+----------+---------+----------+--------------------------+
| 12345678 | Bob S. | Mike B. | (2019-09-16, 2019-11-23) |
| 12345678 | Bob S. | Mike B. | (2019-12-12, 9999-12-31) |
| 12345678 | Jill M. | Mike B. | (2019-08-21, 2019-09-16) |
| 12345678 | Tom A. | Mike B. | (2019-11-23, 2019-12-12) |
+----------+---------+----------+--------------------------+