With regards to flap asymmetry there has never been an incident on the 146 / RJ. The system works and that`s why the flap safety lanes are there. Just don`t turn the Hyd off!. The weak point is the the flap computer and sensors. The drive train was improved with the RJ.
As i stated flapless landing is an issue at high weights (146-300, RJ100) 40200KG is a lot of energy to loose and an approach speed of 190kts +. It never fails when your 36000KGS!
In terms of risk and safety, flapless is a practiced sim training item and well within the scope of an average crew on the worse day. A reduced flap landing is not going to be an issue. Flap 24 is a normal landing flap position and anything else is a bonus. (unless you are going somewhere short like LCY).
I`m sure Brussels airlines will find the problem and fix it. It was always the way that several aircraft in the fleet tended to develop the same kind of problems around the same time normally due to time in service and similar factors affecting the aircraft.