VR locomotion gets crazy when I grab items. Any help?

Hello,
I’m going mad!
I implemented smooth locomotion in the VR Template. When I push the left thumbstick to left or right , I move to left or right; when I push the left thumbstick up or down, I move back and forth. I turn to left and right with the x-axis of the right thumbstick. Everything works fine.
However when I grab items (the small cube, the pistol, etc.) the locomotion mode turns abruptly. When I hold the item in front of me and push the left thumbstick to whatever direction (up, dpwn, left, right) I move always backward. When I hold the items with my hand directed towards the floor and push the left thumbstick to whatever direction, I move upwards, it’s like I’m jumping or flying upwards. Summing up, I always move in the opposite direction of the item I hold in my hand, no matter of the thumbstick direction. When I release the item, everything works fine again!
Can someone explain to me what’s happening, please? Thanks!