Ok, found it...the red cubes should be placed when Economic Sanctions happen...
But it will not return to the Sanctions track during RESET phrase..
Correct. Once either red cube is placed on the corresponding "Aging Weapons Systems" or "No Advanced Manufacturing Technology" space, the rules state they will remain on those spaces and subtract (1) from the adjustment factors of Military Strength and Industrial Development for the remainder of the game. The idea was that the international community would show no trust toward DPRK once they have decided to ignore sanctions for so long--even after they've abandoned their nuclear program.
If you want to simulate a more forgiving UN, you could have these red cubes return to the Sanctions track once DPRK complies with the mandate and dismantles their program (set Sanctions to level zero).