Statistically it seems like it was intentional. Vast majority of transporter malfunctions are either unremarkable or extremely dangerous and cause irreparable harm, if they even make it out the other end at all.
Lots of malfunctions are minor, you'll only lose a few bits from your DNA (the equivalent of acute radiation exposure), but many of the worst ones cause the person to not be reassembled at all or just pattern loss, you'll just never reappear on the other end.