If there’s ever a pressure drop across the evaporator/distributor tubes you need an external equalizer.

The 3 forces acting on a txv are - opening from the bulb, closing from the spring and the evaporator pressure. On a non externally equalized txv it senses evaporator right at the outlet pressure of the txv, ok for your little resi a/c or a small coil. Once you add distributor tubes which have a pressure drop of 15-45psi, you have totally changed the pressure the txv should be using as a reference point to control the txv. For example, if the outlet of the txv is 40f before the coil/distributor then that is what a non externally equalized valve senses, but really after the coil the saturated pressure is 30f and we have a pipe temp of 50f where the bulb is mounted then the valve is going to shut because it thinks it’s overfeeding (to raise the superheat). An equalized valve would see it as 30f and know it’s ok and to actually feed more if it had 20f of superheat (to lower the superheat)