The holes do not appear blocked?
Sleepy is right on. These were actually completely blocked in this case leading to the bone dry magnet. All of that stuff coming out of the tube is being pushed out because of the pressure from pushing the sponge into the shaft chamber. It is roughly a 1/8" tube, which unless water is being forced through at high pressure (it is not in this case) will become biofouled quickly and plugged. Not a great design. It makes me worried about the RD3 cooling/flushing line which is standard 1/4" OD tubing but maybe the pressure differential is larger or the ID is bigger.