Pastes and inserts going to start of track not playhe

When I copy and paste a clip, or insert a one, instead of being pasted or inserted at the playhead position, it's being inserted at the beginning of the track. I'm sure this must be something obvious, but I can't see what it is. I've tried playing around with the Auto Select controls but haven't got to the bottom of it.

[Peter Chamberlain]

If you start a new timeline, or new project, do you see the same result?

It seems to be specific to a particular timeline. If I copy the timeline, the copied timeline has the same problem, but if I create a new timeline from scratch, the new timeline behaves as expected.