Temporal Table Migration from VM to Azure SQL

I recently migrated my SQL 2019 database from a VM into Azure SQL.
I used the MS Data Migration tool, but unfortunately, it wouldn't migrate data from Temporal Tables.

So. I just used the tool to create the table schemas and then used SSIS to move the data.  

Since my existing history table had data in it, I wanted to keep the SysStartDate and SysEndDate fields.  In order to do this, I had to disable SYSTEM_VERSIONING in my Azure SQL database as well as DROP the PERIOD on the table.

The data migration was a success so I re-created my PERIOD on the table but when I tried to enable SYSTEM_VERSIONING with a specified history table, I get the following error:

>Msg 13573, Level 16, State 0, Line 34<br>
Setting SYSTEM_VERSIONING to ON failed because history table 'xxxxxHistory'<br> contains overlapping records.

I find this odd because the existing tables were originally joined as a temporal table so I don't understand why there would be a conflict now.

    ALTER TABLE xxx.xxx 
    ADD PERIOD FOR SYSTEM_TIME(SysStartTime, SysEndTime)

    ALTER TABLE xxx.xxx 
    SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE=xxx.xxxHistory))

I expect to get a successful temporal table. Instead, I get the following error: 

>Msg 13573, Level 16, State 0, Line 34<br>
Setting SYSTEM_VERSIONING to ON failed because history table 'xxxxxHistory'<br> contains overlapping records.

I ran the following query to identify the overlaps but I don't get any:

    SELECT 
    xxxxKeyNumeric
    ,SysStartTime
    ,SysEndTime
    FROM 
    xxxx.xxxxhistory o
    WHERE EXISTS
    (
        SELECT 
    1 
    FROM 
    xxxx.xxxxhistory o2
        WHERE 
    o2.xxxxKeyNumeric = o.xxxxKeyNumeric
    AND o2.SysStartTime <= o.SysEndTime
    AND o.SysStartTime <= o2.SysEndTime
    AND o2.xxxxPK != o.xxxxPK
    )
    ORDER BY 
    o.xxxxKeyNumeric, 
    o.SysStartTime