Amber-encased Vilekin drop/treasure chest spawn rate nerfed?

So I was spamming "Don't Come Back" in order to get enough amber-encased vilekin so I can trade them in for the Anima Weapon quest, and realized that there seemed to be a significant change in either drop rate or chest spawn rate. Over the course of 70 leves I only got 11 treasure chest spawns which equals out to a 16% drop rate per leve, I specifically remember this number being in the 30-33% range before and am not sure if it's because I used to get 2 drops per chest or simply got more chest spawns.

Has anyone farmed Vilekin recently and got the same result?

This will, of course, in no way answer your question, but uh... since I see you have a couple of high-level crafters, the easiest way to get sand is to trade in the Blue Rowena tokens.

70 leves though! Dang that must've taken you at least a couple hours. Yuck.

I haven't farmed Vilekin but I do remember trying to test the theory that Pale Rider can spawn from leve chests back in Stormblood patch 4.3 (it's been confirmed a myth).

The rate of chest spawns was 12 in the 100 leves I tried.