TB Portable adds some new emails at the bottom of old emails

This may sound weird, and I simply do not understand how/why it happens. But for some reason TB occasionally presents new incoming emails at the bottom of an old email. To give an example I received yesterday an email seemingly a copy of an email I previously received 16th April 2008, but with the new email added at the bottom. The new email displays the old emails date, but of course gets a new "Order Received" number.

This happens occasionally, and some times with up to 10-20 emails per day of this type. When it happens it is normally emails from the same original day that are being used.

Quite frustrating to say it mild