Omen of Whittling deleted ANOTHER mod instead of the one highlighted

Had a ring, T1 phys dmg, T1 ice dmg, T5 flat mana, T1 strength, T1 cold res T3 life regen.

First attempt, whittling identifies T3 life regen as the weakest mod by highlighting it orange.

I tried some other crafting options (desecrating a prefix) and the T5 mana mod remained and I got a T1 flat life mod as prefix.

Right clicked omen of whittling again, it highlighted the T5 mana mod and I used a Greater Chaos Orb on it. To my surprise, the mana mod STAYED and the T1 flat life mod got rerolled.

Used another omen of whittling, it again highlighted the T5 mana mod and deleted the T1 ice dmg mod replacing it with a % ice dmg mod.

Pretty much feel like I got scammed.