Clarybear,
I'm reading through this thread and also this related one now and this presents like two different problems.
One being an apparant problem reading the headphone jack - whether this is a mechanical issue truly or not I don't know. Certainly changing the results through use of a contact cleaner, or multiple plug / unplug cycles or tapping on the port or case sounds like a mechanical problem with the port.
Another branch of this sounds like it is a problem with th Realtek drivers - perhaps conflicting with some version of other drivers in Windows, or power management states (coming back from sleep).
I've asked several of our engineers who are using Yoga 2 Pros, and they've not run into this. From the number we have sold, if this was a high volume problem, I'd expect these threads to be bigger by now, but it does seem like something worth looking into. Hopefully we can find a system that will exhibit the problem internally, but as you note, this is intermittant.
If someone in the US has this problem and it was not fixed through updating or uninstalling the realtek audio drivers, it might help to look at your system, especially if this is a pretty consistent problem.
I'd also like to ask those on this thread if they are running Windows 8 or now 8.1 and whether this problem started on 8 or only after 8.1? I'm not looking to put this off on the upgrade, especially for those cases that seem like it is the port rather than the driver, but I'm curious. There was a nother thread where realtek audio stopped working after the 8.1 update and you had to reinstall it as the fix. Just another data point...
Lastly, we are working on the screen flicker symptoms - I believe there is a BIOS update targeted to fix that - still in testing right now, but hopefully available "soon".
Best regards,
Mark