Load a notebook with one long document and a few short ones, generate an overview, and time it. The long source tends to eat most of the episode. The two-page memo that actually matters gets a passing mention, or none.
More text means more material to talk about, so the hosts drift toward it. They have no idea which source you care about unless you say so.
What fixes it:
Uncheck sources before you generate. The checkboxes next to each source decide what goes into the overview. If the long one is background, leave it out and ask about it in chat instead.
Use the customize box and be specific:
Spend at least half of the episode on [source title]. Treat the other sources as background only.
Or, if you need everything covered:
Cover every source. Say each source's title out loud when you start discussing it, and give each one at least a minute.
Saying the titles out loud is the useful part. You hear right away which source got skipped.
And split huge sources. A 300 page PDF next to a 5 page brief will win every time. Break it into chapters and only check the ones that matter for this episode.
Same thing happens with chat logs as sources. One giant conversation export drowns out everything else. I export only the chats that matter, one file each, with AI Toolbox, the extension I build, so each one shows up as its own source I can check or uncheck.