Timeline reverse didn't work as expected

I have a box (a trap) and I want to lift it up and down when i press E using timeline
The flipflop used to toggle the play/reverse works fine.
I press E and the box rises 10 unit, but when I press E again, the box rises another 10 unit instead of dropping down.
I also tried to change addActorLocalOffset to setActorLocation, but the result is the same.
Any help would be appreciated.

Because you are using Add Actor Local Offset which adds to the current offset. What you need is Set Relative Location.

As an idea:
I would use the timeline to drive a float value on the time value between 0-1.
And interpolate between 2 Vectors.*

Create a Vector Variable with Show 3D Widget

And the blueprint would look something like this:

And the result: