Can't extend clip right, white box

Hey guys,

I must have hit some button but I'm trying to extend a clip to the right by just dragging the handle but it only goes so far. I've got plenty of footage left in the source clip. The only thing I've noticed is that there's this white rectangle around my clips that I can't drag past. Anyone know what that white rectangle is?

That white rectangle is the full extent of the clip.

Even if I extend it to the white box, there's still plenty of footage in the source clip. If I delete the clip from the timeline, the white box goes away and then I can extend it correctly. I don't understand why I have to do that in the first place.

I think I've located the issue and it sounds like a bug to me. If you replace a clip on the timeline (i.e. F11) with another clip, the original clip's length is maintained instead of recalculating the new clip's length.

That should happen with a Shift+F11 I think, with just F11 you should be able to extend the clip.