I hope this isn't the case with your dog, but I've found that dogs who learn to undo the chain link at the bottom, then break zip ties, etc. can be inspired to keep trying for that reward of escape.
Securing the bottom may inspire him to unweave the top. Had a lab at my boarding kennel do this. His owners left for two weeks, the first weekend, the dog peeled up the chain link from the bottom to get out. I had a guy come in and weave in a security bar, like mentioned above in another post. He then un raveled the chain link a few rows above the bar. So I had a local metal worker craft a 3 foot high metal plate to put across the bottom. He then clawed and bit his way through the top section of the 5' tall chain link gate.
This all happened during the nights. He was a happy camper during the day and got lots of exercise and play with other dogs. He was just determined not to be kenneled at night. You may have to upgrade your kennel from chain link to heavy bars, but here's hoping not!
Good Luck,
Jennifer