(6) train problem

I've noticed that many of the major delays that have affected the in recent months are because of stalled trains. Within the past 2 months, there have been at least 5 trains that I am aware of which broke down and were reported in service updates as having 'mechanical problems'. In 3 of those cases I was able to catch the stalled train having passed in on the express track or watching it get moved back into the yard (to my shock all were R142A's). I can't think of a line that has 5 or more stalled trains within a 2 month time frame based on the service updates that are reported. I ask, why have so many trains been breaking down lately? I'm curious as to what's happening because breakdowns have been rare before these past couple of months.