A month-by-month look at Citi Bike station maintenance shows that whole station shutdowns are the largest issue. The good news: station malfunctions peaked in March at 630 (roughly 2 shutdowns per station during the month) and have been trending down since. Most station malfunctions required a reboot or a new battery.
Individual dock malfunctions trended up in August though they too peaked in March at 359.
Source: NYC Bike Share monthly reports