Mario, if you select the Tampo group object, the red keyframe ticks will show up in the timeline (it works in the file you posted). You can select it in Outliner or select one of the tampo objects and press the up arrow key (2 clicks) until you see Tampo in your channel box. If you don't see the keyframes, then they might be beyond the range slider's display. As Nem pointed out, you can go to either the dope sheet or the graph editor to delete the keys.