Looks like my DX50's been acting strangely lately. When I'm walking around with the DX50 (hooked to my C5) in my pocket I sometimes (quite rare though) hear a "click"-like sound in either the right or left channel, after which channel imbalance occurs and the respective channel soon cuts off. As of now I suspect rockbox may be the problem, since I tried adjusting my cables as well as switching off and on the C5 and the problem went away after 1) Restarting the DX50. 2) The song currently playing has ended. I suspect it might be a static-related issue.
I encounter that problem with my stack of DX50 and UHA-6S. It turns out it's the cable. Sometimes it's difficult to notice but it can easily slide out thus, you hear a channel imbalance. Best way to isolate it is by using DX50 from HO.