Remove the o-ring when installing the suppressor. You want the suppressor to bottom out on the squared shoulder. This will keep the suppressor aligned with the bore. Periodically check that the suppressor is tight while using it.
The SilencerCo Sparrow has an o-ring that engages a profiled section in front of the threads to prevent the suppressor from loosening. The barrel must be specially threaded for this feature. It also works with the full thread, but doesn’t give the “locking” feature.