I presume we are only talking about the 3.5mm wired headphones issue when it comes to sound problems here???? I've not noticed any other sound issues on the OLED deck.
I've just tested my OLED deck with wired earphones - I never really use earphones so not got around to testing yet. First tried a pair of old wired but pretty decent Sennheiser in ear buds. There is a definite background 'hiss' when using these, even just browsing the menus.
I then tried an old pair of Apple wired buds you used to get free with iphones years ago - and these seem fine, no background hiss! So I think as reported, it is due to the type and quality of earphones you use and ironically better quality ones are more susceptible to having issues.
Given I don't really use earphones much anyway, the fact the Apple ones are ok, and I presume wireless bluetooth ones work without a hitch which I do have, I 'aint sending my deck in....