The M.A.R.C.O unit will break it's coding if it gets angry, and lash out against whoever or whatever made it angry. This will vary depending on what negative tendencies it has picked up from the people around it.
The M.A.R.C.O unit can burn out a few of it's wires causing it's voice to crackle and distort and or causing a short and disabling the M.A.R.C.O unit. Though a wire should only short out if there is someone inside the suit, which has been prohibited for several years.
The M.A.R.C.O unit's defenses will go down and rerouted to other things during the anger period, this can cause serious damage to a M.A.R.C.O unit's internal wiring and components so a M.A.R.C.O unit getting angry should be avoided at all costs.
Learn about a M.A.R.C.O unit's sensors