Extremely slow render with 2 tracks of video at 4K 30

I was rendering a project at 4K 30 fps from 1080P footage. The timeline is set to 4K 30 as well. Right at the end of the video I had a second track of video. The top layer layer was cropped but not zoomed or repositioned. The render was progressing pretty well at an average of 60 fps, but as soon as it hit the area with the second video track it slowed to several minutes per frame and even dropped a couple of frames due to timeout. I was rendering H.265 MP4 when I finally got it to finish. When I tried to use H.265 Quick time it seemed to hang at the 2 video track point. I also noticed a huge slow down for render when it hit the new Burn transition. I have used the burn transition in other projects with no issues, so not sure what's going on here.

Idle suggestion, I have no idea if this will make a difference

When rendering H.265, under "Rate Control" I always select
CQP
instead of leaving it to default to
VBR High Quality

Also I trust both video clips are sourced from e.g. SSD drive and not the second one way off on a network somewhere

Good luck

Your GPU is pretty small for 4K. What happens if you try to export from an HD timeline?

The really weird thing is in normal playback it has no issues while editing, just in final render. Did not have this issue in Beta 4. I will have to try this in regular HD, but one of the reasons I bought Studio was to produce 4K.

Under MacOS, Studio doesn't gain you speed, only features.