Replaced the cold water cartridge on a traditional kitchen mixer tap but still leaks

[luckysh0t]

Tried running the hot tap then checking to see what the water temp of the drip was after and it was cold so to me that means the leak is from the cold water valve side. Replaced the cold water ceramic disc cartridge but the drip is still there (even when I turn off the mains but don't fancy keeping it off long to see when the leak dries up).

All the YouTube tutorials seem to be about replacing the cartridge to fix leaks so I'm turning to you guys for advice on what else I should check?

 

[Aquarius]

A photo of tap maybe helpful. Perhaps it’s the hot valve leaking?

 

[steadyon]

Rarely worth replacing only one cartridge, they tend to go more or less at the same time in my experience.