DVP-NS400D DVD player not outputting LFE channel?

[RL]

I have a Sony DVP-NS400D DVD player, which is an older player, but has always worked well and has the 5.1 analog outputs to hook up to my Sony STR-DE335 receiver.  However, I can't seem to get the DVD player to output a LFE signal to my receiver.

The DVD player has a feature to display the audio output information on screen of the disc currently playing.  When I select "AUDIO" from the disply menu, it shows the "DOLBY DIGITAL 3/2.1" message, indicating that the DVD player is reading the 5.1 channel information from the disc.  However, the "LFE" indicator is almost always outlined in a broken line, indicating no LFE signal is being output.  (I have verified this by holding my ear against my subwoofer while playing a disc, and no sound is coming from it.)  This is all explained on page 49 of the operating manual.

On rare occassion, the LFE indicator will actually switch to a solid line for a few seconds, and then switch back to the dashed line.  This makes me think that at some points, it is actually picking up the LFE signal.  I've tried multiple DVDs, specifically ones that I know for certain are recorded in Dolby Digital 5.1 channels.  (They have it labeled on the case.)  With some I can get the LFE to show solid for just a few seconds, while others I never can get any output of the LFE signal.

Is there some setting somewhere that I might be missing?  I've tried switching the subwoofer setting off and back on from the setup menu, but that did nothing.  Is this maybe a software glitch?  Is there way to reboot the player?  Or is it maybe finally on its way out?  Everything seems to work fine otherwise, and to be honest, I'm not sure if it ever properly read the RFE signal.  I've tried the "reset" function from the setup menu but that also did nothing.