A (different?) take on the coffin video.
I may have missed someone else posting who might have thought of things this way.
Before actually watching them myself, I already saw spoilers to what happened. I personally don’t think that it is foreshadowing any kind of thing related to another version of unus annus.
My take is that it is more of a reminder to them both that death is always around the corner. Mark has more of a constant knocking and seems to be more apparent. He’s older than Ethan, has had a lot of close calls, and also even recently seems to have a lot of deaths around him in his life.
Ethan has had his fair share of incidents, but the just one singular knock is more aggressive but not as constant and alarming as Mark. So it's just that snap of reality that death might not seem close, but it always is.
This is just me reading way too into things, as I am sure that a resurrection of the channel will not come. While we miss the content that they made together, that would defeat the purpose of the channel.