Re-tensioning blinds?

[Daisymini]

Has anybody got any advice on re-tensioning my blinds? When the temperature drops the blinds will not go down until it warms up. As the winter comes the problem gets worse.
I have the blinds with the top fly screen and thermal bottom and it's always the bottom one that sticks.
I'd like to avoid taking the internal framework off but if I have to I will.

 

[Robmac]

I think you may have to remove the inner frame Sue.

Is this any help?