You should make sure the sensor bar isn't blocked by anything and is flush with whatever surface you are mounting it on. I'd say you should try to take the TV that is 4 ft off the ground and temporarily put it like 2 or so feet off the ground and see how that helps.
I am the owner of a Wii. I say this because my sons fight over it, so I tell them I own it and that seems to settle the fights. But I don't play it very much so I have a tough time evaluating a problem my son says we're having.
We have 2 TVs (actually, we have 5 TVs, but only 2 that we have or will probably consider hooking the Wii up to. The TV in the Living room is larger and up on top of a tall piece of furniture. The bottom of the TV is probably almost 4 feet off the ground. The other TV is a bit smaller (but still at least 20") and is in my older son's bedroom; it sits on a small wooden TV stand so that the bottom of the TV is no more than 24" off the ground.
My son (the older one whose bedroom the other TV is in) tells me that when the Wii is hooked up to the TV in the living room, any games that use the Wii remote don't work that well. I have observed that the cursor jiggles and it's harder to be accurate with it than I'd like. I guess this seems to not be as much of an issue when the Wii is hooked up to the TV in my son's room, but I really don't have enough experience with it to be able to tell if this is really a true problem or if my son just wants the Wii in his room. He's been asking us to move the TV in the living room onto some piece of furniture that is lower to the ground, because he's convinced it's a height-of-the-TV issue. So I know it's not just that he wants it in his room, he really thinks moving the TV down will fix it.
Has anyone else had this issue? In both rooms, we have the little sensor bar on top of the TV -- so in the living room it's above my head, it's so high up. I just can't see why that would matter, though. The piece of furniture we have the TV on is an antique that I have no other place for, and I also like having the TV up high so we can see it in the kitchen. It's very heavy to move even to experiment with, so I thought I'd find out if anyone else had any ideas before I did anything else. Thanks in advance if anyone knows any tricks that might fix this, something else that might cause it besides the height of the TV, or if they can just confirm that it really might be an issue.

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