For specific details, certain spoilers exist in this response, please be advised.
Unlikely for my experience even if it makes sense from the perspective of “what” the bug is, because my second trigger was after Revenant Dragon. Not her gate, not the chest. It was right after her battle and speaking to the Caretaker, and her chest was bugged and so were all my safety check altars (as expected). Cutscene for this only had Mythal Dragon dialog without any major involvement of the dagger. Perhaps something to do with unlocking options (this one event sets up a lot for the ending too) or the Caretaker. Also to note as of today (cleaned up everything), boss did not trigger the bug anymore thus giving the potential of a more random or undefinable triggers. Ive placed all my update notes throughout this thread in detail. Which now makes sense why Emmerich and Bellara are so relatable. Sorry i too ramble. 🤣
Either way, the dagger is the what but the why may still be up in the air unless i missed a dagger scene in the entire Revenant Dragon fight i did a few times now. 🤔 (not being sarcastic btw. I may have literally missed it. 🤣)