I travel a lot as well and up and until about the latter part of last year, i was getting the male profile button pushed on the scanner a lot because invariably a box would light up around my bra strap.
I typically do not dress ultra-femme to travel but casual (jeans, boots and t-shirt or button up shirt, with a leather jacket if it is cold) and definitely not male mode, also i have breasts and i didn't really hide the fact that i did. So it was all a bit perplexing to me.
It never caused much of an issue, usually the agent would be like..."what's back here?" and i would say..."I'm wearing a bra" to which they would say....ok have a nice day. One lady even said... "oh sorry dear, you have a really nice day " after a guy agent patted my back.
One guy responded one time "really?" (like no dude im kidding you its not a bra ). I started wearing brighter lipstick when i travel and a bit more makeup overall, as my hair has been growing out as well, this whole treatment has largely faded, but i suspect it will happen again some time.