The robot returns to the charging station each time to clean the pads. This keeps the pads moist. At the same time, the internal water tank is filled to moisten the pads during cleaning. It looks as if the internal water tank in the robot is no longer being filled and therefore the moistening of the pads during cleaning is no longer guaranteed. I would use compressed air to blow through the water channels in the robot. There is probably something clogged.

Something stuck internally that might limit the waterflow might well be the case, it's a very good point, but Instead of using air, as suggested, I would use a syringe (without the needle) and water, squeezing the syringe really hard. When I got the robot it wasn't loading water at all and the syringe was the only method to make it work properly.

Just remove the needle from the syringe, remove the rubber cover that covers the connector in the station for the water tank, and then put the tip of the syringe in and just squeeze hard. You might need to repeat the process until you are seeing a proper flow of water from the base of the station where the robot loads itself.