Did you follow proper procedure and set up standards first? Bars and tone? Did your editing system flag any part of the signal as out of spec? Are your cameras and systems set up for Japanese black level, or American? Japanese black level is darker at actual zero than American at 7.5 IRE units, so check your waveform and vectorscope displays.
IF the last 2 sentences had totally unfamiliar terms for you in them, we may be on the track of where your problems started.
My guess is though that at the point where you moved your program to DVD, something may not be right. Could you describe in detail the procedures you use and the way the signals flow in your system? From camera thru to final DVD, please. Somebody may pick out the part that creates your trouble.
OTOH, the station could be at fault as well. Particularly with a DVD, you don’t know if they are going to digitally transfer the pristine original quality mpeg files into a server… or play it in analog composite off a $30 Walmart Apex DVd player into a router or patch panel, from there to a betacart or another server… doing who knows how many digital/analog conversions along the way. At any step of that signal chain, something could have been set wrong. Like a game of “telephone”. We may never know what or where.
The best you can do is make sure you have maxed out the quality in your own signal chain to the best of your ability, measured against an actual standard of reference. Those bars and tone need to be actually related to the material that follows them, such that the brigtest white in the bars is the same as the brigtest part of the entire program. The black of the bars needs to match the black level of the program as well, or if the tech adjusts to bars’ black level, but your program is darker, he’s going to over-compensate. If your monitors are not all likewise calibrated, what looks gorgeous on your monitor may be horribly out of spec. If you’ve done that correctly at your end, you can’t be responsible for someone else not calibrating to the bars and tone correctly.