At this point you really need to do some experimentation.

Do you regularly see the same TSOs? If so, it may be possible to ask one of them to do an experimental patdown, where they swab each thing / each part or your body individually and see what in particular triggers the alert. Or you may be able to approach the FSD at your airport and say you are having problems regularly triggering the alarms, and you need some help figuring out what you are doing to cause the problem.

Alternatively, you can try eliminating variables one at a time... do you wear any aftershaves or colognes? Use a particular hand lotion of styling product? Hand sanitizer? Strong smelling detergent? Do you fuel your car with diesel? If you suspect your wife's fertilizer is causing the problem, ask her to store it in a different location (or even better, switch to an organic regime!), or park your car outside on days you plan to travel to the airport. Is there a lot of construction near your house?

Worst case, you could buy a set of travel clothes and shoes and change after you arrive at the airport.

Final question, why are you always selected to go through the ETD? Is it "random selection"? Do you opt out and get patdowns? Is it possible that your name is flagged for extra screening?