You have changed your radio gear so you should be able to rule out radio gear as long as you are on 2.4 . If this is something that is happening only to you then it must be something that you are doing wrong . Its hard to say why it only happens after you have been flying a model for a long while . We don't know your maintentince habits . Do you keep a watch on your linkages for slop ect. How do you store your planes?. Is there a possibility for something to move changing the C of G ? Are you flying glow fuel and does this happen closer to the end of a flight? That would indicate a tail heavy condicition . Maybe you need to balance using a more acurate method than your fingers . I am not so sure it is balance unless something has suddenly changed the balance . It may be a combination of things . Have you ever had a chance to fly one of these planes again after one of these incidences with any success ? If you have and it flys okay then pilot error would start to become suspect . Is that a possibility? If you have not had the chance to fly one of them again afer a crash, then you should have at least had the oppertunity to closly examine the elevator system on one ore two to see why it failed . I have seen a lot of crashes and often the tail section is still intact.