this player regularly pops every 2 weeks so much that the national u21 holds him under control.
here is his skills:
Jump Shot: respectable  Jump Range: strong  
Outside Def.: average  Handling: average  
Driving: average  Passing: respectable  
Inside Shot: inept  Inside Def.: awful  
Rebounding: mediocre  Shot Blocking: atrocious  
Stamina: pitiful  Free Throw: average  
Do you mean every 2 weeks in outside d? If so, I'm not surprised as his outside d was probably much lower than the rest of his skills (until now). I think you will find that his outside d training is going to slow now that it has caught up with the rest of his skills.
Also, what is his height?
I think there is a bug problem whit him, because my other guard pops almost every weeks...
There are too many variables here to say that there is a bug. As I said before, so many things affect training. 
also, he get ever about 65/70 minutes a week...
Why? You only need 48 minutes at his training position to get full training. Any more is a waste.
Run of the Mill Canadian Manager