4k dynamic link AE comp scales down in very poor render quality (jagged edges) when exporting in HD

 Dynamic Link has a lot of mysteries under the hood (at least to regular users like us), so I'm afraid I don't have any insight into this one. I often perform a Render and Replace when I'm done with a comp anyway since rendering or exporting my timeline always slows once the DL clips are hit.

It doesn't sound like you're doing this, but the first thing that comes to mind that could cause this is if the Preview Settings in your Premiere sequence settings dialog are set to a lower resolution, you've rendered your timeline, and then check the "Use Previews" box while exporting.

That's something that a more qualified Ae expert would probably need to help with. @David Arbor  ... or a staffer ... @mattchristensen  ?

Thanks for the suggestion, yes I have. Premiere has no trouble scaling down the graphics when I import them into premiere as ProRes 4444 with alpha. But with the same graphics linked as dynamic link clips I can't export to a lower resolution without getting terrible aliasing. Maximum Render quality was always checked in all of my renders testing this issue and I've been coming back to this project for weeks, the problem still persists. Only usable workaround is to render at the original resolution and downscaling them to HD with AME after the fact.

Do you have Max Render Quality selected both in "preview" and the export dialog? That forces high-Q rendering most noted in diagonals.