You can tighten a loose nutsert back up yourself. Find a bolt that fits it that will fully thread in with about 3/4" extra threads. Run a nut on that bolt and then screw it into the nutsert. when the threads are fully in the nutsert hold the bolt head from turning and tighten the nut against the nutsert being carefull not to strip any threads but you have to crank it down as tight as you dare. That will swell the nutsert back into a tight position.
You can install nutserts this way also although a pop-rivet gun made for nutserts works best. A washer that fits the bolt well compliments things when doing this.