Media is linked in bin, but still showing as offline on timeline

I have a project with some media that is linked but still showing the red "Media Offline" graphic.

To troubleshoot this, I deleted all but one clip from the project and have made it available here: WeTransfer https://we.tl/t-39AJwYKh3q

• The media is fine in the project, I can double-click it in the bin and play it in the source window.
• It is the same clip as on the timeline which I can check by right clicking the clip on the timeline and selecting 'reveal in project'
• if I 'match frame' the clip from the timeline, then I can see the video content in the Source window and play it fine there.
• The timeline thinks that the media is offline, when exporting it says "this timeline contains offline material"
• If I right click the clip on the timeline, the 'link media' option is grey'd out.
• I can make the clip on the timeline offline. If I right click the clip on the timeline, the 'link media' option is then not grey'd out. But then linking the media still results in the "Media Offline" graphic in the program windows and it fine in the source window as per all of the above.
• If I do a 'replace media' and select a completly different file, I still get the same result. Which is why I share the project because you can re-link it to any media and you will get the same result. (make offline on project open and then do the 'replace media' option)
• I have tried re-setitng Adobe preferences, deleting all cache folders etc. Still the same result.
• I have tried oppening on PC and Mac.

I could of course re-edit the whole thing, after all, match frame does work and I could just drag the clips all back to the timeline one at a time. But there are about 200 offline clips throughout the one hour timeline and I would rather not have to. Anyone got any ideas?

Stephen