sigma 70-300mm f4-5.6 dg macro sticky aperture blades

[lesz42]

As above, have used DOF preview to try and free it up ( 50 odd times) sticks 1 in 8, then takes a few goes to return to normal, any other ways to remedy this issue?

 

[a1ex2001]

Take it apart and clean it, not worth a pro repair as a new lens will be cheaper so you may as well try yourself!