Problem with wf-1000xm5

Hello everybody,

I bought the m5 about 3 weeks ago after my xm4's left earbud stopped working, but after only a few weeks of use the left earbud is way lower in volume than the right ear bud. The strange thing is; this is only when I have both earbuds in, if I only put the left one in my ear the sound is fine. But when I insert the right bud it lowers the volume of the left bud.

This is very frustrating after only a few weeks of use, I've googled similar problems but the only thing I can find is that they could be dirty, which i find hard to believe as the 'filter' has nothing on it whatsoever.

The problem occured after I finished a run, could it be due to water ingress from the sweat?

Thanks for your help