As Stefan has pointed out it's your basking set-up causing you problems!!
I like to have a neat line of lights (like Stefan's),if you have more than 2 in a line then you find the middle one is usually hotter surface basking temp than the outer surface temps., that basking spot flood is what charges his./her turbo up.
Use bulbs that push the heat downwards, hals push the heat downwards, also the bigger the bulbs you use the greater the burn off in the viv of humidity, also the greater the gap between the bulb & basking surface the more air is pulled under & air dried/humidity burned off.
If you use a reflector this also pushes heat down, silver backed reflector are more efficient.
I like a greater gap between the light bulb & basking surface, this allows the monitor to pose rather than crawl under the lamps, if they have a high basking spot flood (160f) this allows the monitor to spend less time basking which means they aren't breathing the drier air for as long.
These light are mounted high above the ply surface & located at the top of the cage, the lower reflector has the bulb set the same height as the rest>
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