Bug with omen of Whittling

https://imgur.com/a/EDw5m33 can someone explain to me why when i used the omen that takes lowest tier mod away when you chaos orb it took my t 6 ES and not my t4 Leech physical as life? just cost me 20 div

Omen of Whittling targets the lowest "level" modifier, it doesn't say "tier" anyway. "Level" is based on what the required ilvl is for that modifier to appear. Unfortunately this is not possible to see anywhere in-game and it makes the text on the Omen very confusing and easy to misunderstand.

For your item the ES mod was the lowest required ilvl at 47. The leech mod is actually very high at 68.

craftofexile.com is invaluable for this type of information

Its not a bug, its how it works. It replaces the lowest LEVEL mod, not lowest tier. Before using always check the mods on your item, in your case rings: https://poe2db.tw/us/Rings#ModifiersCalc