Davinci Resolve runs fine on Ubuntu, but doesn't like my Insta360 ONE R?

I’m working on a video project and I’ve dropped all the footage for it in the project file of Davinci Resolve for the first time.
Footage of my Sony A7S III, 4K 25fps, h.265, mp4 of course.
~ Sony RX100 MII, 4K 25 fps, h.264, mp4
~ Sony ZV-1 recorded through my Ninja V, 4K 25 fps, H.265, MOV
~ Insta360 ONE R, 4K 25 fps (aspect ratio 4:3), H.265, mp4.

The project frame has been set to 25 fps as that’s what all the camera’s were shooting in.
Because of my high end PC, packing the best graphics card on the market today (RTX 4090), everything runs smoothly.
However, the recording of the Insta360 ONE R is running at 13 fps.
When I’m checking the attributions of the footage in Davinci Resolve, that’s what it says: fps is set to 13.
When I manually correct it and tell it that it is in fact 25 fps and then click OK/apply, immediately it says ‘‘media offline’’.

Does anyone know what is going on?
I don’t understand what could cause Davinci Resolve to be convinced the footage was shot at 13 fps and should therefore be played back.
It’s not playing back at a different speed either. The speed is normal, the frame rate is abnormal.
When playing back to footage in VLC on the same computer there is no issue.

Now I’ve tried to delete the clip in the timeline and adjust the framerate from 13 to 25 again.
This time it doesn’t say ‘‘media offline’’ but when I drag it onto the timeline again the footage is being played at twice the speed after I’ve adjusted the framerate from 13 to 25 in the attributions.
Davinci Resolve is convinced the footage has been shot in 13 fps…