Sticky keys on Magic Keyboard

Some of the keys on my Magic Keyboard that came with my 18 month old M1 Mac are sticky while others are a bit "grungy" - i.e. don't feel very smooth when you type on them. In contrast, the keys on the old wired keyboard I bought for my 2018 iMac all work perfectly.

I am not aware of anything have spilt onto my new keyboard and it hasn't had a massive amount of use.

I've tried using compressed air to clean out any grit that might have got into the keyboard but at best this has only made a marginal difference.

Any suggestions of what else I can do? Would an Apple store be able to clean it for me or are they just going to tell me to get a new keyboard?