18:15.53 is the 5000m world record for M70. An 18:34 split during a marathon does seem awful fast.
I guess it hasn't occurred to any of you numbnuts that his timing chip was malfunctioning on those sections?
Timing chips are simply RFID tags. The timing mat energizes your chip when you pass over it and reads the ID number. Either it successfully gets a reading or it doesn't.
There is no possible way the timing mat could get a reading from your chip when you're more than a few feet away, never mind half a mile down the road.