I need to remove failing Trex boards due to manufacturing defect. Any suggestions on removing the screws?
Screws tend to like to snap off, your best bet is to hope that they snap between the wood framing and the trex, rather than just the head snapping off.
There really is no "trick", either the screw will back out or it won't. Probably the best advice is to have plenty of back up, properly sized, driver tips at the ready, and to really clean out the heads of the screws before you start so the driver tip gets a full bite. Use low speed and care when starting the removal, once the screw is loosened, you can increase the drill speed.
For the screws that snap off, you can use pry bars to slide the board over the screw. For the screws that snap off, if you need to save the trex, then use a sawzall to cut the screw between the framing and the trex. If you don't have to save the trex, simply break it off and worry about the screw afterward.
Removing old composition decking and trying to preserve them don't go hand in hand. The old Trex boards will be damaged to the point of being unusable.
If your intention is to install a new top deck, then rip the Trex and screws any way you can. This is called demolition.