Multicam clip - not including whole clip

Does anyone recognise this: Creating a multicam clip from the video clips and 2 additional sound tracks. Two of the video clips are 21 minutes each (it’s an interview) and there’s a GoPro ws which is much shorter (2 min). When I create the multicam clip (right click>create new multicam clip using selected clips) using sound to sync, the GoPro and one of the video sync fine, but only a 5 second section of the second long video gets included. I am using proxies, but can find no faults there.
Any thoughts ?

Resolve 20
iMac : 3.8 GHz 8-Core Intel Core i7

Make sure the In/Out point option in the Multicam dialog is unchecked.