Yeah i said long time ago that bgvp has serious problems with quality control and manufacturing. It was with dm6 and seems became even worse with dm7. Mine dm6 after tfz 3 is unusable and is in the box somewhere. After I harsh and unnatural treble Tfz 3 is uncomparably better in my opinion. But if someone was lucky and got better dm unit. Then it could be different story.
I have 2 pairs of dm6 and I think they sound great (Final Audio E tips and ISN copper cable). I bought the first set from BGVPs own store on AliExpress and they are superb.The second pair I got from Penon, they lasted a week before the left iem gave up (no sound). However after about 3 weeks of BGVP/Penon emails they replaced them and I now have 2 sets that are both excellent. Penon were brilliant throughout the return, it just seemed that BGVP were the slow party in the chain, whether it’s their customer service that’s slow or they were low on stock I can’t say, but it was sorted and took nearly a month to replace a faulty week old iem.