So, very quickly, confirmation bias is when something does or does not happen that confirms your pre-determined expectations. Example: Farming Timbershade 81 times without the lead dropping leading you to call it bugged - only for the lead to drop on the 82nd kill.
I say that as I want to be clear that I am not saying that some of the lead drops are bugged, but I would like to highlight that some are being very very very shy - those that drop from Daily Reward Coffers.
In particular, Deadlands Dailies, West Weald Dailies, and Crafting Dailies. Having obtained and dug up all the other pieces of antiquities, for my 2nd and 3rd iteration of the antiquity (collecting lore entries), I am left missing the leads that drop from the aforementioned coffers. I have opened hundreds of coffers, for example the WW music box I completed the 1st iteration within a week, and obtained the 2nd iteration of the other leads several days later, and have been opening 3 - 6 coffers a day since (well into the hundreds) with no lead dropping.
I do my best to avoid confirmation bias, but this lack of drops is not helping. Would be much appreciated if ZOS could look into this and at least confirm the leads can drop.