Nested sequences (multi-channel setup)

I'm trying to setup a workspace for editing a 2-channel video installation.
I'm editing my two individual channels with 4K Material in two HD timelines. Since I'm working with a lot of different source material and it fits my workflow best, input scaling is set to: "Center crop with no resizing" meaning I have most of my 4K material set to 0.5 zoom at the moment to fit the frame. so far, so good.

To preview the two channels playing in sync, I set up another "HD" timeline twice as wide and drag the respective timelines onto it. Here's where the problems start. The nested timelines play back just fine but they show all the 4K source clips in the original 4K size meaning 50% of the image is cropped. I don't see a way to change this, since zooming the nested timeline resizes the already cropped image (which is expected behaviour).

I'm wondering if this is supposed to work like that as I do not see any advantage for the nested files to preview the source material like this (without any adjustment options). Am I missing something here? Making a compound clip of all the clips in the original individual sequence doesn't change this behaviour either. Any tips would be appreciated.

Can you show us? A screen grab maybe?

While preparing a test image to properly show the issue, I accidentally found out what causes the behaviour: it's the Timeline proxy mode setting. When turned off everything behaves like expected. But once it's set to 1/2 or 1/4 the issue arises. Additionally interesting: It does not happen on "standard" 16:9 Timelines. I'm working with two 4:3 Timelines (1440*1080) and it looks like this:
(The "2Channel preview Timeline" visible in the screengrabs is 2880*1440)

Proxy mode setting: off


Proxy mode setting: 1/2


(Clips stay centered of course, the offset is only due to my skewed test image)
Setting proxy mode to 1/4 prompts a further zoom in.

Since I'm running low on hardware power I'm usually working at least in the 1/2 setting, so would be great to have a solution for this. Otherwise I'd have to reduce the size/bitrate of my proxy files to a point where I can flawlessly edit with proxy mode off.

it's the Timeline proxy mode setting.

I've seen other reports about that being problematic, and have seen a couple issues using it myself.

My best advice is, don't use it. Solve playback issues some other way.

Jim, thanks for your reply and insight! At least now I know it's a more widespread bug and can stop trying to fix it somehow. Looking forward to a fix in future versions.