I have a 10-year-old asphalt shingle low-pitch roof on my house and many shingles no longer adhere at the seal strip. Water can get under the shingle and seems to be leaking through the nail holes to the wood (I don't have an attic, but water drips from the fascia vent). Could the shingles be faulty? Does anyone ever go after the company under the 25-year-guarantee. Any suggestions?