I suppose fitting drawer fronts could be a bit tricky to even them up and have a consistent gap around all edges. One tip I use is to take a pack of playing cards and use them as spacers.
Depending on the brand, 4 or 5 cards make approx 2mm, I sit them at each end on the bottom to give me my height. Then to centre the drawer front between the face frame I slide the drawer front over to one side so it is tight and slide cards in the opposite end until they are snug. The next move is to take the cards out and then half them, fit the halved bundles into each side of the drawer front and it should be perfectly centred between the face frames.
A quick tip that works. Enjoy