Take off the pedals first, then remove the screws underneath one by one. Don't forget the one hiding under where the cable comes in!
When you remove the top part have a good look around and know what you're looking at. If you hold down the base at this point and put one of the pedals through its travel you will see how they work. This is where the problem lies!
The potentiometers have been set incorrectly and all we have to do is turn them through their travel to the correct location so the pedals engage them at the appropriate point.
Make sure you've gone to ts.thrustmaster.com and downloaded the firmware updater. In here there is a calibration tool so you can connect your T300 to your laptop/pc and see exactly where the potentiometers need to move. Connect your pedals to your pc before you start fine tuning, and press the pedals through their full travel too. Now you can start fiddling with the pedal box. Note that the top half presses the pedals about an inch or so before they should start to engage. This is part of the reason you need to adjust and re-adjust until you get it right.
Just so you know, mine pedals are set perfectly now. 100% free of deadzones, instant engagement on touching them and full travel on both. Perfect. However, I won't lie, this took 5-10 attempts of opening and closing the pedal box fully to achieve. You must have patience!
But trust me it's worth it.
Setting the potentiometers takes some trial and error but the most annoying part is getting the top back on. The most effective way I found is to post the pedals through the top half then turn the box over so the pedals are touching the floor (preferably carpet). Carefully line up the two half's at the bottom part of the box and apply a small amount of pressure while guiding the brake spring into its correct location. It needs to go over the nobble on both the base and the pedal itself. Bit fiddley but essential. When everything is lined up properly place your knee in the centre of the base and apply pressure while guiding the two halves together. Now they're in place you have both hands free to insert screws. Screw in as many as you can from this position then remove your knee to do the remaining ones low down.
Job done!