In most cases, a chime/beep while driving with the top up and locked means that the controller reads the rear bow being unlocked. There are cases where the rear bow lock has developed enough play that it will show "locked" at first, but the striker gets pulled up enough to make the micro switch signal "unlocked" once the canvas has been pulled tight enough when latching the top in the front.

Note that the micro switch on the rear bow lock is electrically 'normally closed', and this is the reading the controller needs for a closed lock. This means, the metal lever that pushes the micro switch pushes down on the micro switch when the rear bow lock is open and it produces an open circuit. When the lever releases the micro switch enough, the switch will be electrically closed again. This happens before the lever actually fully releases the micro switch. Typically, the lever just about touches the micro switch when the lock is closed, but it does not push down far enough to trigger the switch into the electrically open position. When there is extra play in the rear bow lock, and you just locked the top in the front, then the lever can be pushed down far enough to trigger the switch again.

Unlock the front and open the trunk. Then lock the front and observe the lever on the micro switch of the rear bow lock. If you push up on the lever just a little (such as to move it away from the switch), do you hear the switch clicking? If so, then you found the culprit. If so, then bend up the lever a little bit - not more than a millimeter (or 1/32").

Klaus