Annorax

Hi everyone, I live in MA and have an in-ground, vinyl lined, DE filtered pool. I had it professionally closed recently. Over the past week or so, I've noticed that from one of the closed return jets, I see a few bubbles coming out of it. I do see a fairly big crack in the jet's face plate where one of the screws goes in so I think that might be the issue. I called the pool guys back and they said it should be OK, but I am concerned that over the winter, water will leak in and crack the lines. The previous year I had to repair a cracked line right near this return jet so I have been cautiously watching it. I've put some Lexel around the crack and face plate as a temporary way to stop it, but I'm doubtful it will hold the entire winter and I'm also not sure how much water has already leaked in. I called the pool guys back to replace take a look, possibly to replace the face plate and reblow the lines, but they are busy so I'm not sure when they can come back. Some people say a little bit of water in the lines is OK, but I'm not sure if a crack in the face plate can cause the lines to fill over time. They put 1 gallon of antifreeze in the lines but I'm not sure if that is enough to stop a lot of water. What do you guys think, is there a concern here? I've also tried to use food coloring to see if there's a leak but I didn't see anything move. Do air bubbles always mean a leak?