Extremely Slow Exports - v25.2.23

I work for a small internet media company, we produce and distribute video podcasts through platforms like YouTube. Some of our shows are recorded using software like Riverside or Streamyard. The past 2 weeks, we have utilized Riverside to record a 3-camera show and after downloading that video/audio from the site, laid it into Premiere for sync/edit. 

We have overlays for ISO, 2-box, and 3-box looks and I have been nesting the footage with it's respective overlay to make the edit easier since I'm manually cutting cameras. To be clear, I have a 3-box next, a 2-box nest, and 3 ISO nests. None of the nests contain audio. 

Export settings are:

• Video: H.264 | 1920x1080 | 23.976 FPS | VBR 1 pass 12Mbps 
• Audio: AAC | 320 kbps | 48Hz

The file size is 5GB. Again, we are an internet media company exporting out small file sizes relative to anything that would be used for broadcast (I have worked for 2 major networks and have experience with huge file sizes and very long renders/exports).

The show's TRT is approximately an hour, but it has been taking Premiere 2+ hours to export. I have tried Encoder and it's not any faster. Does anyone have suggestions on what could be causing the slowdown? 

Solutions we've considered:

• The nested sequences
• The overlays (since they are static and stay up for entire show's TRT)
• I have noticed 1 of our 3 cameras is from a mobile device and has a variable frame rate. I did try re-exporting the timeline minus that camera and the export time was still 2+ hours. 

Any suggestions are appreciated.