Oil pan leak

So after a routine oil change, my dealer detected what they called an upper oil pan leak. After ordering parts, I brought my car in for the fix. They've now had it for two weeks. Apparently, it's quite a job to disassemble everything to get to the seals in question. After five days, and a road test, they discovered that it still leaked . The tech had to re-do the entire job. I'm still waiting to hear back as to results and as to when my car will be ready. My previous DTS had the notorious half case leak. I'm beginning to think that GM can't build an engine that doesn't leak. The car has 28,000 miles. Has anyone else had this problem? How common is it? I'm not impressed that everything has been removed and re-done twice.