Thanks for posting. It's possible the springs you purchased were not the correct strength fo your sash. Can you tell me how heavy your sash is?
I used two springs on each side, a 9.5 lb and a 3.5 lb for a total of 26 lb.s. The 3.5 lb is the bent one. The sash weighs 22.8 lbs. I am now operating it with 3 springs - two 9.5's and one 3.5, and it works fine.
I have this setup on 9 windows now, this is the only one with a problem, so far.
If you did not get my earlier reply, the sash is 22.8 lb.s.
I wonder if the lubricant used might be the problem?
Thanks. I did wonder if the tension difference would be an issue. I will use your recommendation from now on.