Fused Mouth Disease/Syndrome?

Hi everyone, I have a strange issue with a goldfish's fused mouth. He's a normal comet feeder but I've had him for years so I have quite an attachment to him. He got a fused mouth a few months ago but he's been living quite fine. I feed him and even though I've never actually seen him eat, he's alright and he breathes. I tried surgery twice. The first time I found a cartilage/plastic kinda thing jammed vertically across its mouth, I was able to cut it in half (fully anesthetized) but that didn't work. During that time, I also found that a membrane or skin of some sort grew in between its lips. The second surgery a week after, I tried cutting it but I am not sure if it's open. If anyone has some insight or experience with this strange disease, please help me! My little feeder might pass any day now :[