The oneplus3 cannot be relocked as it wrongly trusts test-keys. It also has public EDL firehose files available allowing anyone to flash it arbitrarily even when locked or further dump ram or userdata.
sadly, unless you have this recent agesa update you can no longer load recent microcodes due to this fix
which very well means quite a substantial amount of models whose vendors don't provide a bios update for this (since it goes back to zen1) will not be able to load any future fixes via microcode