Before seeing Mikail’s suggestion, I got tired after trying MySQL8 on three different PC’s and got the same issue. So, I moved on to use PostgreSQL10.6, and which worked out perfectly without any complaints. Luckily these two are very similar in structure and Admin tools.
Now the only problem is finding a good way to remove old data in Postgres since it does not yet have the MySQL events functionality.
OK. I went back and applied Mikhail’s answer, which is OK as workaround for MySQL8.
The correct method is to follow the above link is MySQL8 doc on assigning fractional part to the time values. When I used the DATETIME(6) type the DBExport worked fine with 6 fractional values for the SECOND. Problem fixed.
Of course, if you still encounter the duplicate Primary Key issue, apply Mikhail’s fix.