The problems with GenSets are starting to surface now that they have been in use for a few years. Up here in the Great Grey Northwest, Tacoma Rail has a GenSet that looks as new as the day they got it -- because it sits at the shops 90% of the time. I don't know if it has issues; maybe the mechanics can't find the key to wind it up ?!? I do know I've never seen it out running without being MU'ed to another " real " locomotive.
Are the Gen Sets becoming lemons ??? Perhaps they are too technical for an industry that began with link & pin couplers and brake staffs ??? Remember that Santa Fe's first road diesels, EMD's now legendary FT, were often sent out with a riding mechanic onboard to fix the stuff that would fail during a trip. Look at the current offerings from GE and EMD / EMC / Progress Rail; now the RR's have to send out a computer programmer whenever the engine burps !!! Gen Sets are more electrical than anything else, which can't be good in an operating environment that features heat and vibration, the 2 worst conditions for anything electrical. Remember also that many GenSets have been forced upon the RR's by the various Smog Nazis ( LA, Bay Area, Houston ), so they have to be used and seen.