Astra: Failed and partial renders

When I first looked at Astra a few months ago, it said it would render 5 minute segments, so I divided my video into 5 minute chunks. Today I subscribed & went to render the first section, but it turns out it would only render 450 frames at a time. So I turned on Detect Scenes. It then rendered some scenes, but others were left in a “Partial Renders” state, and I can’t download them. So what am I supposed to do?

Do I have to divide my video into little 18 second sections and render each one?

Plus I spent a bunch of credits rendering that first section, but I can’t use the result as it now has unrendered holes in it.