Hi
Geoffrey what drills have you done?
Drills that can help this common fault are:
1- Go back to hand spotting the skill. but do it from a step lunge.. handstand block (making sure a nice lunge and reach into the HS) then spot and shape the handspring.
2- Do the handspring down from an elevated surface. So like doing the handspring of a panel mat. Feet on the mat and the hands are on the floor. This forces! the gymnast to reach down and lunge on that leg in order to put the hands down. otherwise they will dive and well it wont be to pleasant as you can imagine.
3- Re evaluate your gymnast entry into the handstand. Generally if you entry into the handstand is no good it will transfer to the handspring. If there are faults (like closing of the shoulders, depresed scapulas, lazzy first leg, weak push of the lunge leg etc. then spend the time to fix them.
Hope this helps. I think the best way to go about avoiding the problem in the first place is to
1- make sure the handstand entry and handstand block are solid (as in that problem is not present)
2- Handspot the handspring from a lunge..dont let them run at it until basic prep is solid
3- Under basic handspring prep spend time working the entry (its really boring for you and gymnast but it beats the frustration of your gymnast not getting it right)