On: Deaths at a California skydiving center, but the j...

[LorenPechtel]

Since it says they tangled I don't think your case #1 could be relevant.

I have never skydived and have no interest in doing so but from reading the other comments it seems like there's another possible scenario:

Main deploys badly. They jettison the chute which deploys the reserve--but the jettisoned chute is hung up on something, doesn't actually jettison.