Raid red borders

[fossil frost]

So usually there's a chance for them to drop and one purchasable per week right, considering that vow is "Farmable" when on rotation now.. Would each run have a chance at dropping red borders randomly?

[open grail]

Yeah if you farm encounters you have a chance of getting a red border during rotation

You can’t get a red border aside from the weekly first one from the chest at boss, nor can you get the secret red border chest thing more than once per week