Tyre stepping/Sawtoothing?

Had a good check over the condition of all 4 of my tyres today. Needless to say all 4 will need changing next week. I've opted for a set of Kumho ku39. The passenger rear tyre has aggressive tyre stepping (also known as sawtoothing) where the inside tread blocks have worn unevenly. This makes it sound like a wheel bearing has gone, which it hasn't as the rear brake discs and pads are new.

I don't want to be spending £240 on a set of Kumho's to then have the same problem. Does anyone know what could be causing the stepping? Driver's rear has worn perfectly. Its just the passenger side.

Any advice/knowledge is much appreciated as always