AirPods Max one ear louder than the other

The left side of my AirPods max sounds quieter than the right side, it feels like the higher frequencies are rounded off. I have reset the airpods, repaired, tried on multiple devices and also checked that my L/R balance and EQ settings are set to neutral. Even tried it in mono and it leans to the right.

Haven't had these £450 headphones for too long, they were working last night - I put them in the case and set them on a desk that has not been touched until now. I put them in and notice this issue. My ATH-M50s sound fine, it is not a problem with my ears.

I have tried all the advice for the other questions about this to no avail. I have cleaned the headphones inside. Not that any dust could've got in since I put them away given they were in the case.

What can I do? Very frustrating for such an expensive product I have kept safe.