I get some of the same kinds of random glitches with my DVD-1000. The remedy on my unit is to periodically turn off the master switch, rather than leaving the unit on standby. This resets the unit to the default and whatever you specified in the setup.

Keep in mind that Denon's entry level DVD players are basically modified Panasonic units that are made by Panasonic (or their outsource manufacturer). Pannys are well regarded entry level players, but I believe that Denon specifies different output circuits and modifies the firmware (which has been a problem with a lot of their early production DVD players). I've not been too impressed with the build quality of my Denon and my particular model has had bugs in the firmware in earlier units, but the picture and audio quality are excellent.