I use the Marlen 30fr catheter that has a bullet shaped tip and, I believe, slightly smaller holes on the side than the Medina. I have never had a kink when where the holes are located when intubating, but then I never force it in. If it feels like I have “hit a brick wall”, I try to relax, change the insertion angle, or try again a short time later. The only time a catheter has kinked at a hole is when I am not careful in putting it in a small case for use when away from home. I get at least 3 months and sometimes 6 months of use out of a catheter. Your slight leakage at 8-9 hours is likely a result that your pouch has reached its capacity. When your pouch is close to capacity, you will have a feeling of fullness, or slight cramping. It does not sound like you have an impending valve failure.
Bill