More video clips in Color tab than in Edit tab. Why is this?

Windows 10 x64

Ok, I've probably done something stupid, but I can't find a solution via Google or in the manual.

My problem is simply this...

In the Edit tab, I have 13 clips on the timeline.

When I switch to the Color tab, two of the clips are duplicated (they are sitting next to one another) so that I have a total of 15.

What have I done?

Thanks!

D

Sorted!

When I magnified the timeline to its maximum, there were two, split-seconds, bits of clips on it, which were clearly visible in the Color Tab, but not in the Edit Tab.

No idea how they got there, but sorted now.

Phew!

D.