I will never understand the recommendation to recirculate the air by putting the intake in the skimmer cup. All you will do is suck in foam until your co2 scrubber turns into a skimmate locker, eventually filling up and causing the very issue you had. It’s happened to me as well. Best way to use a scrubber is to simply let it draw room air or outside air. Not recirculating. Squirt 20 ml or so of water into the bottom of the scrubber every day to keep it humid and replace the media if ph drops below 8.
Mine works flawlessly. I think that may depend upon your skimmer and how aggressive the skimmate is being produced. Also, the skimmer cap on my EuroReef helps to prevent skimmate from entering the return line.