Premiere Pro CC 2019 - Lag / Unworkable

Hi all,

I'm having some serious issues with editing some simple video - I have about 5 clips that I want to splice together (a music cover video), a mix of 4k and 1080p which would be exported at 1080. I haven't experienced any issues before the last update. I haven't even added them to the timeline and when I preview them in source window they lag so badly it's completely unusable, especially as I can't cut and input clips.

Computer specs:

• OS: Windows 10 Pro 64-bit
• Processor: Intel Core i7-4790 CPU @ 3.60GHz (8 CPUs)
• Installed memory: 8.0 GB
• Hardrive: 500 GB (SSD)
• Graphics Card: NVIDIA GeForce GT 720 2 GB

Project specs:

• Premiere Version: Premiere Pro CC 2019 Version 13.0.2 (Build 38)
• Video Rendering and Playback: Mercury Playback Engine GPU Acceleration (CUDA)
• Files: 4 videos (total size 4.81 GB) + 1 audio master (36.7 MB)
  
  • Playback absolutely fine on VLC, Quicktime and Windows Films & TV

I have already tried:

• Switching between 'Optimise rendering for:' Performance and Memory
  • Premiere Pro has 6.4 GB of RAM dedicated to it - neither option made any difference
• I have read other people's issues and I have unchecked 'Enable accelerated H.264 decoding' (and restarted my PC)
  • This made no difference
• I have restarted my computer, imported all the footage again and still have the same issues
  
• I have opened a new project and loaded old footage (same mix of 4k and 1080p formats) which I have already previously edited and I had the same issues - both with preview source lag and timeline lag (even with the playback resolution at 1/8th instead of my usual 1/2 quality playback)

I have read that you can make proxies of footage - I do not want to do this as I shouldn't have to. This is a new issue and one I've not experienced before.

Please help - I would greatly appreciate any advice and do let me know if I can provide any more information to help resolve the issue!

Cheers,

Alex