The best method is to find out which doohickey doesn't like to heat soak. You need some method of systematic "testing" by spot cooling. In the olden days before the ozone hole, I'd take a refill can of r12 and go around spraying doohickeys, one at a time, with a start try after each. I've since used r134 refills, a garden sprayer with ice water (real good with a fine stream for getting at hard stuff), canned dusting air (takes too much), Liquids or refrigerants are the best options.

Not responsible for advice not taken...