Ignoring any kiosk hardware reliability issues, power supply interruptions or airport WAN glitches, it's unlikely that Navitaire (Ryanair's IT provider) is guaranteeing Service Levels significantly in excess of 98%.
30 days*24 hours*60minutes*2% = 14.4 hours of tolerated outages per month.
Even 99.9% reliability (which is fairly realistic and achievable) equates to 72 minutes a month which - Sod's Law being Sod's Law - will affect your operation at its most vulnerable pinch point at the most inconvenient time imaginable.
It may appear on the surface that Ryanair has no contingency plan.
They do.
If there's chaos in the terminal because people can't check-in/drop their bags, they'll claim that it's an issue beyond their control.
Simple as that