Copy and Paster Keyframes (Keyframe Editor doesn't work)

Hello!!

Almost every time that I use the command copy and paste keyframes in the keyframe editor I have problems.

It doen't work properly like After Effects.

I do CMD C to copy and when I press CMD V to pase it does't work.

I have to close and open motion again to work for a short time, or restart my machine.

I use Yosemite 10.10.3

Motion 5.2.1

Imac late 2013

16gb memory, SSD 240

Everything is up to date.

Is just me or there's somebody facing this problem?

Sorry for my english.

Thanks.