^^^ That would be my guess. Proper torque is important for all critical fasteners.
If you intend to work on critical fasteners, get and use a torque wrench, it is the only way to know that the fastener is at the proper tension. All fasteners have a yield point, so it only takes one significant over torque event to permanently ruin the fastener.
When installing new wheels or spacers, the shape of the flat surface that touches the hub often differs from from the old one. The face of the hub should be cleaned of any rust, debris, paint, etc, so the new wheel/spacer will sit flat/solid to the hub. If there is debris between them, the chance of the connection failing is high.
I have run/installed tons of spacers, never had an issue. I clean the hub surface, torque the spacer lugs to 100tf/lb, install the wheel and torque to the spec for the type of lugs. Drive 50-100mi, remove the wheels and recheck torque. The lugs should not move, if they do there is a problem, debris on the mounting surface, stretched studs, etc.
I would never run loc-tite on wheel studs. Properly torqued lugs, that are in good condition will never come loose,,, EVER. Using adhesive on the threads makes the torque recheck useless and it is the best indicator/conformation of a solid connection. If the lug is glued to the stud, the stud could be stretching, the spacer could have shifted, etc, causing the connection to be loose and still click at torque spec due to the adhesive. If the lugs need to be removed, will most likely ruin the studs, due to the force required to turn them off exceeding the yield point of the fastener.