This has been discussed several times for vertical spindles. We have found it sometimes depends on the holders and how hard they are working; some jam frequently some do not, some do it when they are taking heavy cuts for a long time.
Keep everything squeaky clean with a very light film of lube oil; no gunky coolant residue.
A fix that we installed on two machines was an air tank downstream of the machine regulator. If you look at the air pressure gauge during a toolchange the pressure drops dramatically because the airflow is restricted through the regulator. A tank provides a large flow of air when the tool eject cylinder is operated and the pressure drop is much less so the cylinder operates faster and stronger.