Can you see if the bubbles come from the top, bottom or sides? The location of the source gives me a lot more to work on. Most bubble issues not related to new salt mix or additives will be due to depth and air adjustment, never have more than half the intake submerged, never close the air more than 1/3rd of the way. If the air has been closed a lot, unplug it, raise it so 1/4-1/2 of the intake is submerged and open the air all the way. Plug it back in, work with depth first and close the air as little as possible. It sounds contrary to logic but as you restrict air, you increase water flow so the bubbles are traveling on a lot stronger water flow and more exit. If everything was reassembled correctly there are not many other possibilities, what usually gets assembled incorrectly is the plate with the pump on it is seated too low, that plate has notches that line up with the side locking tabs and it sits so the top of the plate is in line with the top of the skimmer back, the perforated bottom plate goes into the second groove from the bottom, not the very bottom, these are the main areas I see reassembly mistakes that can cause it to not close properly so bubbles exit, mostly the sides, top is always too deep, bottom is usually air is too restricted.