The Braava uses a peristaltic pump that relies on the tubes being clean. Using non-approved cleaning fluids can block the tubes or make them 'sticky' and degrade the efficiency of the pump. There are YouTube videos on how to overcome this problem. It is not a simple procedure and would, I imagine, invalidate any guarantee. If it's under guarantee contact iRobot. I had a motor failure that iRobot diagnosed over the web and replaced for free. They were very helpful.

I had the same problem. I cleaned filter. I also cleaned the jets at the front both with a fine stiff brush (as recommended) and with a WaterPik dental high pressure water spray flosser. Fixed the problem.