How old is your male? If it's his first season breeding, he may be still trying to figure things out. I've found that males that have bred before (seasons before) tend to not waste much time in locking, and you're probably seeing more mature males.

Here are tricks that I've employed - save a shed from any other snake (another female will do) and put it in with the couple.

Wait for a weather system to roll in - and pair them - barometric changes tend to put them in the mood.

Put them together when he's in shed. Put them together when she's in shed.

Heavily mist them both when you put them together.

For what it's worth, I don't drop temps on my heat tape either.