Sansa Clip Plus Dimming Display

[yell0w_lantern]

A few weeks ago the display on my Clip + went dim.  Plugging it in to a charger or computer USB port made it readable enough to up the brightness.  While that did not help, flicking the device with my finger helped. I surmised that something was loose. I couldn't really find anything obvious on inspection - no fallen off components - but I couldn't rule out a bad solder joint.  Eventually, flicking it stopped working and I had to keep the case partially open at the bottom and compress the sides to get the display back to full brightness.  Now even that is not reliably fixing the problem.  I tried replacing the battery today but that did not help.  I re-flowed the solder on the pins from the OLED to the board without benefit either.

At this point I am not sure how to proceed.

Is there a known cause for this? I've seen other people mention the dim display online but I haven't seen any component-level answers, just "hit it" and "turn up the brightness".