Observation regarding TVs and HDMI Cables

I haven't seen this anywhere, and I tried a forum search, but nothing came up, so here goes. In case anybody has the same issue that I had, the setup I have in my truck is a laptop that is hooked up to my TV via HDMI cable (I don't do this when I'm at home). Whether a desktop hooked up to a TV the same way would have the same issue is beyond me as I have no experience with this, but in any event, when you start the simulator, load the PMDG 747-400, and start the flight, the only sounds I would hear are the engines. No flap lever, packs, APU, or anything else. I have determined that if you run FSX in full-screen mode and you hit fly now, the TV will go blank briefly as it switches into another mode (not sure if different resolution or a different refresh rate). If you do NOT run FSX in full-screen mode, the TV won't go blank, and all the sounds play just fine. HOWEVER, if you then try to put FSX in full-screen mode, the TV will go blank briefly as I described earlier, and the sounds for the flap lever, packs, APU, and everything else with the exception of the engines will disappear once again. The only work-around I have determined if you want to stay in full-screen mode is to load your default flight first before selecting the PMDG 747-400. The only caveat is that if you switch to the desktop for whatever reason, the TV blanks out again as you go back to the desktop, and if you go back into FSX, you'll lose the other sounds again. Of course, if I just use the computer without hooking it up to the TV, this problem doesn't exist, but I just don't have enough space in my truck do actually do that, as the laptop would be hanging over the edge of the table.

By the way, trying to select the TV as the sound source in the FMC doesn't solve the issue, and trying to switch the sound source to the computer and back to the TV won't work, either.