my drone just back from DJI after repair from fall from 100ft on its 3rd flight on 1st day of ownership was tested yesterday, flying at 100ft height and 300ft away from me  i tried the RTH command, it took off vertically at full speed, managed to cancel the request and manualy return it, anyone had this problem?

RTH is usually very reliable and it's behaviour is most likely your unfamiliarity with RTH operation than a malfunction.
One common cause of confusion is that the RTH height you set is in metres regardless of the general setting in the app.

The simple way to confirm exactly what happened and if it was a malfunction is to look at the recorded flight data.
Go to http://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions there to upload your flight record from your phone or tablet.
Come back and post a link to the report it gives you.

Yeah post your log so we can see what was going on. When was the last time you did a compass calibration or imu calibration?

You probably had the RTH altitude set higher than you were at.  It would have returned when reaching the  programmed height.

I am sorry to hear about what happened to your drone. Please contact our DJI technical support team so that they can create an escalated repair case. Thank you.

See the first line of Labroides' post and also Alabama's post.  

RTH is supposed to ascend to the minimum RTH height first thing.  It appears from your description that's what was happening.  

Actually, first thing is it rotates and faces homepoint.  Second thing is it ascends vertically as needed - PROVIDED you don't touch the sticks (if you touch the sticks, it will abandon the ascent and move to the third thing).  Third thing is it travels horizontally towards homepoint.

GO CAPS

From a distance the ascension may have looked like it was going away vertically, sounds like all was well but the flight log would help clarify things