Went through last Wed. Emptied my pockets of everything. Belt off. Watch off. Etc. Usually that's enough to ensure that it doesn't go off. This time it did. Full body scan and pat down. If this is happening as often as it seems to be given the posts on here, it can't be helping the security delays.
The scanners are set to go off every ninth or tenth person regardless. Sometimes more randomly, sometimes less randomly. This happened regardless of you having taken all precautions to prevent this. You may just have been unlucky.