My guess would be that the tech installed an incorrect voice coil, or did not center it properly during installation. When you tested the woofer before sending it off to be repaired, did you test the tinsel leads behind the terminals all the way up to where they come thru cone? when you push on woofer with your hand, does it make noise or have resistance in it's movement? Push on it ONLY when there is no power being fed to it, meaning even if you are not playing music and the amp is idling with the speaker switch on. They will have current flowing thru them in this case, and your assessment of the movement will be that they will feel tight as well. So, what I mean is that when the amp is on and speaker switch is on, they are being fed current in the form of "white noise", in which case the woofer will be resistive in movement because of that. It should still be silent and not make any noise or rubbing sounds. I have found things such as a backing tape on the outside circumference of coil sheath, an edge of the securing tape had come loose, causing a noise during movement of coil in gap.
So, giving you an educated guess, providing the tech you used did not use a coil that was not suited for your woofer's coil gap, I would have to say that he/she did not center coil correctly during installation, and it is binding in gap, which will eventually lead to it failing again, once it has rubbed the enamel off the exposed winding. Send it back to them, would be my suggestion.
