However, there is a problem with channel 40 with the 2160A that the Visio TV handles fine. Channel 40 has 4 sub-channels: 40-1, 40-2, 40-3, and 40-4. A scan using the Visio TV finds these channels and using its channel up/down works fine in that I can go from 40-1, to 40-2, to 40-3, to 40-4, and then to 45-1.
The 2160A also finds these channels, but when I use its channel up/down it skips over 40-3 and 40-4. So I can go from 40-1, to 40-2, and then it goes to 45-1. I can enter either 40-3 or 40-4 directly on the 2160A and it tunes into them correctly, but when I use the channel up/down it skips them. For example, I can enter 40-3 directly, use channel down to get to 40-2, but when I use channel up I get 45-1 instead of 40-3.
Does anybody know why this is happening, and is there a solution?
Yes, it sound as if you have one or more duplicate channels vying for a slot in the tuner?.
The solution might be a "Map Your Own" procedure, as described here.
Use the resources there to find what station/network/content should be on those channels and see if there is some OTHER channel with the same content, or that is listed in one of the resources. If you can find one low-numbered and one high-numbered channel with same content, try deleting the low channel using the Manual Channel Preset menu.
The success stories in that linked file might also give you some clues as to what might be going on and what they did about their similar problems?
You may even find that 43.3 and 43.4 station/network/content is just being "re-mapped" to different tuner slots (channels) in your Mag's tuner, which is a "hybrid" (switched analog/digital) tuner compared to your HDTV's tuner, which is an integrated tuner (all channels in sequence with no switching reqd).