Do these use 2.5 mm or 3.5mm?

Bought the PC38X in Dec 2021. Stated on the item - and still on the product page - that they have a 2 year warranty. For the last 2 weeks the balance is not working anymore, and the sound ends up in just the R side or L side of both. It especially happens when I adjust the volume knob. I tried different cables and devices, same problem. The Drop rep so far has tried to lie to me several times, saying that: 1) I should try things I already mentioned I tried (they never read my first e-mail carefully) 2) That they're not in warranty anymore (bold lie, as per the website, and they confirmed the order date is within 2 years) 3) That they're in warranty, but no stock is available, so would I accept a $20 Drop credit instead (again a bold lie, they're available and IN STOCK on the website) Why does Drop think it's ok to blatantly not honour warranty on a defective product, and why is it ok to make-up random excuses every step of the way?

...and that's a good thing.