Erratum!
The lock losses are not "Defined as a Metatron node making a transition from a higher state to down or init" but rather as a Metatron node transitioning from a nominal state of ITF_LOCK (META_ITF_LOCK_index) to DOWN or INIT. Indeed, they are basically defined according to flag channels DQ_META_LOCK_LOSS_{DoF}, which are themselves defined as explained.