People have been declared legally dead, only to wake up at various points past it, such as the morgue, during autopsy, in the casket without an autopsy, already buried.

This bit of evidence doesn't really support the overarching theory. Since the 1980s there have been only a couple dozen of these incidents, and they for the most part always have one common denominator, the affected persons being very old.

It can be harder to accurately find the pulse and other life signs on the elderly, and people aren't as likely to really search for signs of life on someone who looks as fragile as a terminally ill elderly patient.

The vast majority of transplants are from young healthy people who were involved in traumatic accidents, and thus wouldn't really be subject to the Lazarus effect.