Hi all,
Id try teaching the "take and give " as a seperate exercise...Once he has got that then try to join the 2 together.Once your dog will "take" the article then Id say "hold" and gently apply pressure to the top and bottom jaw...With tonnes of praise.Once you have got it with him sitting in front of you then try it moving...So if he is running towards you , say "hold" and make sure you only take it from thier mouth...never pick it up from the ground , if he wants you to have it he will give it to you !!
I hope this helps , my GS did something very similar as a pup(very frustrating) but she now retrieves the dumbell beautifully...
Cheers Brock