What's Pete fixing in this pic? Its the position of the awning pull down strap. 

Don't have the strap all the way up the end of the roller - like in this pic. Have it as close to the centre as possible. 

When rolling your awning in, first relase the roll up mechanism, them slide the pull down strap toward to the centre of the awning, before allowing the awning to roll up.

You will get a more even roll, and reduce stretching one end of the fabric.