That risk is far too high and the performance in recent years shows there is evidence to back the case.
It is completely unfair on passenger paying full fare to be delayed, it also leaves Irish Rail open to significant refund/compensation to delayed passengers.
The Mk4 fleet even at its worst in the early days was 10,000km per 5 minute tech failure, the Japanese DART fleet is at 130,000km, 22k is somewhere upwards of 60,000km
RPSI is down in the hundred's of km
Total number of failures I've had personally account to 1 MK2d (gen van, actually cooled down inside with the AC off!), 1 Mk3 (battery, bussed to destination), 1 Mk4 (MU cable, some physical encouragement was used), 2 DART (brakes) in 30+ years, only two of those required assistance to get moving again. I have a 50% success rate of seeing a steam engine haul a train with the RPSI.