as hemi rick said. very, very seldom do inserts back out with the fasteners, although over the years using them, i have had that happen. usually, when this happens, it is because the helicoil threads were tapped improperly during the initial installation. it could be the wrong drill size used, the tap used incorrectly, such as [mostly with] it being tapped by hand, and thus not being perpendicular to the surface, or several other items/practice[s] not being up to snuff. another real problem some have, is not breaking/removing the installation tang after installation, or using a too long fastener, each discussed item causing the fastener to severely bottom out in a blind hole, and in a through hole, if the installation tang is not broken off clean, the tang remnants can snag on the fastener threads during removal, causing the coil to try to stay with the fastener during removal. on other derivatives of inserts, the locking action can be interference thread fits, locking compounds of differing types, or other means of securing the inserts, preventing the inserts from coming with the fasteners during the removal process. this, by no means, indicate these inserts can not be removed. they are relatively easy to remove with a little practice/patience. i forgot about the custom insert i made one time to fix a 4"NPT thread on a gas well meter. this insert was made from a slug of 6" round steel. the male threads were 5 1/2"x12 with a 1/4" thick flange that screwed into the aluminum body, and was retained with 4 - 1/4"x1/2" long set screws. it was sealed on the OD threads with an o-ring at the flange in a receiver groove, plus thread sealer/pipe dope on the threads. the internal 4" pipe threads were sealed in the normal manor [pipe dope]. if removal was required in the future, additional inserts could be purchased with the retainer screw holes in excess around the flange in case the original four flange holes did not line up. a new o-ring was included as well. this then became a running change to the meter bodies we made, and lasted for many years until production ceased on that body type.