What happened at the start of Star Trek: The Motion Picture then, if its so safe?
When the power on the receiving end of the transport failed, the transport computer on the Enterprise was unable to maintain the pattern integrity of the matter stream. This is akin to catastrophic degradation of the pattern. Kirk said “Boost your matter gain, we need more signal!” – perhaps indicating that the ACB could have been used to reconstruct the pattern. In any case, the hand-off appeared to have been nearly complete when the transportees began reforming on the pad. Since the Enterprise could not handle the transport, the matter stream was sent back to Starfleet HQ, in the hopes that enough of the pattern remained in the ACB to reconstruct them at the sending site. It wasn’t, and the subjects died shortly thereafter. ….
