TLDR: My right dynamic driver appears to be dead. How can I potentially check and fix it? I purchased my Mangird Tea (6BA+1DD) in May 2021. It worked fine for me until this week. I noticed that the right side sounded much quieter and less pronounced in bass notes. I tried several methods below...

I sticked with my M40x with ZMF's pad upgraded a few months and now want to try something new and higher tie. M560 and HE400i is my choose in around 200$ (HE400i used - like new in Amazon), but I don't have a change to listen and compare those. Any suggestion for those cans?