Hi

Without being able to do a full assessment I am just suggesting areas that may be contributing to your recurrent injuries without being able to definitively say it for you.

Recurrent hamstring injuries can be hard to shake. how quickly after feeling no pain are you getting back to full sprinting and full training? Following a strain strengthening needs to be done slowly and gradually over a fair period of time. give yourself at least a 6 week window to get back up to pre injury levels.

It may also be a flexibility issue. Have the flexibility of your hips, lower back and even thoracic spine evaluated. If these areas are stiff and not moving freely your hamstrings will be working harder than they need to be, harder than they can safely achieve especially while healing.

Hope this helps