Reefrat: The aircraft was not being flown correctly. It appears the last part of the approach, when they were lower than their discussion height, was flown too slowly. This resulted in a loss of control when they initiated a go-around. Never be low and slow.
Additionally, a public transport aircraft should be remain controllable at all times, when on the ground or in the air following the failure of any engine. So if an engine failed or spooled up at a different rate to the other, that still should not have been a problem. But a turboprop engine producing reverse is generally a terminal event (as ever, there are some exceptions). Because if this, interlocks are fitted to prevent reverse selection in flight. But when one engine does produce reverse thrust in flight, it will not produce a "bucking bronco." Something far more violent occurs: one wing stops flying, drops and the aircraft yaws and rolls after it. This is often unrecoverable even from thousands of feet (Luxair 9642), let alone close to the ground. I do not believe it is flight tested and there is no requirement to do so. And to put things in perspective, the decision height for a Cat I ILS is generally in the order 200' AGL.
Why this crew flew below the decision height on multiple occasions is the interesting question. Whatever the reason/s, there are certain failings we all suffer from. Amongst these, you'll often find that crews are often their own worst enemies and push things too far. Others work for dreadful employers who won't pay them for diversions or late arrivals. Others expect them to perform tasks which can only done by licensed engineers. Others work without proper supervision. The AAIU have prepared a very interesting report on this one.