Gewa Piezo Pickup w. remov. cable

OK it's been stuck on my instrument for the best part of two years but I almost always play unplugged, so this pickup had hardly been used, until the other day, when I noticed the metal ring at the top of the input had come loose, causing the signal to fail intermittently as well. So now I've had to pull it apart to figure out how to fix it. As you can imagine, I'm not really enthusiastic about buying another, so if I can't fix it, I'll have to find another solution. Sound isn't massive either, in fact, plugged into a Marshall MS-2 mini amp, the acoustic instrument is just as loud as the amplified sound, although the sound is authentically reproduced, that much I must say for it.