I have had luck removing the nock and sticking a drill bit down the shaft a shade under the inside diameter of the shaft. Then hold around the fletches with the heel of the palm or your thumb over the hole and insert side pointing up so the bit is back on the nock end, then whip the arrow down and use the KE from the drill bit to impact the back of the nock and break it loose. Slight heat sure usually helps though, but I have been successful without, I usually stick the back of the drill bit in first to not potentially damage the insert if that's your desire. Putting a little cup of solid tape is smart too to prevent the insert and drill bit from possibly flying out when it does break loose.