Weird Offline Media Problem V14.3.0.014

I'm currently editing on a high end gaming laptop until I get my studio built.

Yesterday a staff member managed to run over my laptop destroying the screen and motherboard.

The hard drives survived so I transferred the complete Resolve folder structure to the new replacement computer.

C:\ProgramData\Blackmagic Design\...

My video files are stored on an external hard drive so I made sure to assign the same drive letter as was used on the old computer (G:) before starting Resolve.

I started Resolve and the project loaded fine, but some of the clips are showing as Offline, even though they play fine. I also notice the audio waveforms are not showing, but again the audio plays fine.

Some clips show "Media Offline" at the beginning of the clip, but normal thumbnails after that. See attached picture.

I would just put up with it, but I just discovered that when I render the timeline some clips will show 1 frame of "Media Offline" at the edit point.

I can also sometimes see this when playing the timeline. It's quite intermittent though and happens at different spots.

I've tried deleting optimised media and the render cache, but there is no change to the problem.

Anyone have any suggestions for me to try?

I can also sometimes see this when playing the timeline. It's quite intermittent though and happens at different spots.

Here's a screen capture that shows the problem while playing the timeline. This is slowed down to 10% speed to make the problem more visible.

I just tried exporting the project, renaming the folder where all the media resides, importing the project and relinking all the files and there is no change to the problem.

So I then imported my most recent backup from about a week ago, relinked the media and still the same problem.

Now I'm extremely worried. This project represents 6 weeks of work and I'm dead in the water.

I was concerned before about losing a week's work, now it seems I'm going to have to start this project from scratch if I can't find a solution.

Some information about my system:

The old computer which worked fine:
ASUS G752 Laptop - i7 6700HQ CPU, 16GB RAM, GTX1060-6GB GPU, Win10 Home

The new computer:
Alienware 17 R4 Laptop - i7 7700HQ CPU, 24GB RAM, GTX1070-8GB GPU, Win10 Home

The media hard drive is a Toshiba USB3 external drive. I've been using these for several Resolve projects on the old computer without issues.