What would cause my line sets to equalize in cooling mode?

Try to find a good heat pump guy and not the "fool" you called before. The problem could be a faulty reversing valve, faulty compressor, refrigerant charge, bad metering valve or piston or any number of other conditions. Most guys just attach hoses and add more refrigerant without looking for the REAL problem. They know very little of what happens or is supposed to happen at any point in the refrigeration cycle. Many of the problems associated with an A/C unit or heat pump can be diagnosed without the use of a set of gauges and a bottle of refrigerant. A real service tech will stop, listen and touch before getting the tool box. This reminds me of a real life story that I observed many years ago. The tech replaced the compressor, contactor, high and low pressure controls, thermostat and control transformer, each on different calls only to find out that the real problem was a burned out control fuse. True story. And this guy had years of experience. my 2 cents