Acura Integra SE 1995 Shift Shock

When we first start the car if we try to shift into reverse or park the car does an extremely hard shift or shift shock. The motor mount and transmission mounts are fine. We also flushed the transmission. The strange thing is if you let the car warm up for 5 or 10 minutes it doesn’t do it. It is not temperature related either. Only when the car is first started. This is an automatic transmission. Please help us figure this out.