[GAMEPLAY] Frostfang giving 5 gold instead of 10

I was playing as Karma support and bought Spellthief's Edge. It gave me 5 gold per enemy hit, ok. Then I upgraded it into Frostfang when I got to 500 gold... It still gave me 5 gold per enemy hit, while the tooltip clearly states 10 gold.

Screenshot attached.

I have another similar one if you're interested.

The bug didn't only affect towers, but also champions, with both abilities and autoattacks.

it's not a visual bug, I really had Frostfang.

I haven't tried reproducing the bug, but I think I explained the steps well. it happened once in my last game.