All cartridge style HOBs are designed in such a way that when the media is clogged, water overflows over the spillway back to the tank. AC does not have the spillway design so when the foam is clogged, it pops up. But the instructions tell you to adjust a screw to level the box to prevent the foam from tilting one side and dripping off. A human error but also a bad design, along with the O ring, and this is why I don’t use AC.
I'm not familiar with this style of filter. What brand do you use?