The Q400 is not unlike the BAe ATP... the product of an ailing company, desperate to get a new aircraft into production, who simply took a successful design and stretched it (a lot). Add new avionics and systems and hey presto, a new aircraft!
However the ATP was a disaster... we used to call it the Advanced Technical Problem. It was so bad that BAe Prestwick sent a brace of engineers up to our hangar on permanent deployment, to try and sort them out. Being as horrible as it was, it found few customers. The same was true of the Q400 until flybe managed to achieve some level of reliability - took them quite a while though.
The Q400 is similar. Take a great aircraft, the Dash 8-300, and stretch it, add lots of new bits etc. Trouble was, it was all done rather badly and it wasn't long before the first batch were being returned to Canada for "re-manufacturing" - in other words, adding all the metal they removed to save weight, which, it turns out, was needed to prevent the structure from bending! New stringers above the cockpit area, plus some wing mods, are two I seem to recall. The process took three months per aircraft. No wonder SAS got so bent out of shape over it!
Bottom line, the Q400 is built to a (very cheap) price, and therefore not very strong, and many of the components not very reliable. I lost count of the number of times we would push back, all would go dark, and the crew would announce that they were having to reset all the computers... or the F/O would turn all the lights on for his pre-flight checks, and promptly flatten the battery. And then there was the Q400 that needed a new generator after less than 100 hours... in fact quite a lot of parts were replaced after very few hours indeed.
Expect to see a lot more returns to base...