Think we had a similar thing on Vero 2. This advice might help you: HDMI-CEC some buttons not working on Vero2 that do work on Pi2 - #21 by Dilligaf. It can occur on Samsung TVs because Vero configures itself as a ‘player’, where as a Raspberry Pi considers itself a ‘recorder’. On Samsung TVs the button assignment depends on the role the device presumes.
Sam