Adding a PNG to timeline KILLS render speed. Advice?

I recently edited a 16-minute video in Resolve 17.1. When I did the first export in the Deliver panel, it took about 20 minutes. No problem.

Then I realized that I forgot to add a logo to the video that was supposed to be in the top corner. A PNG with an alpha channel.

I dropped the PNG on the timeline and went to export it again. This time, render time jumped to 5 hours!

Does anyone have any advice for dealing with this? I used to edit in FCPX, and adding a PNG to a timeline didn't have this much effect on render duration.

Right now, I'd be better rendering it without the PNG and then adding that using FCPX so my computer isn't tied up for 5 hours. But surely there must be a better way?

What format is the footage you are editing? Is it one of the ones that support Codec Passthrough and do you have Bypass Rencode When Possible checked in the Render Settings?