Cannot Find An Answer For This Anywhere For Years

Hi, looking for help here, I have an issue that started years ago that I cannot find anyone that can help with. My issue is with my 18'X36' inground pool, I have a half moon shaped sitting area in my deep end that has jets in the calf and back area (you just step off into the deep end). I also have jets on either side of my stairs at the end of the pool in the shallow end. There is a air intake (to create bubbles) at the spa area and one at each side if the stairs, the problem started one year when I opened up the air intake to create bubbles coming out of my jets and water poured out of the air intake. This happens at the stairs and the spa, blowing the water down thought the air intake opening will blow the water out and create bubbles but as soon as I stop blowing air in the water pours out again. I have no leaks that I am aware of but sometimes after playing with the return, spa and stairs valves by the pump I can get bubbles in the spa area but only if I close a couple jets and it's very seldom that I can get this to work. I have purchased a new pump but this did not fix anything and there does not seem to be any blockages. This worked very well for the first year and a half but have had the issues for 6 years now, pool is 8 years old. The installer said it was a design flaw but how could it be a design flaw if it worked perfectly for a long time? Any ideas anyone?