74" rear window blind help

[GMH]

I have re-strung a narrow 2-string blind in my 5vr and it works absolutely perfectly. I am currently trying to repair the 74" wide by 45" high 4-string night-only rear window blind. I have re-strung it with proper string cross overs and played with the tension. I can only get it to raise about 10 inches and then it binds and the bottom rail seems to arch up in the middle. There is only one spring that all 4 cords are attached to. I have searched all over and most tech help is for day/night blinds. Also, all of the help and videos are on smaller blinds. Has anyone managed to get a large blind like this to work again? The DW says it used to work properly when new.
P.S. The 4 plastic bushings where the strings enter the bottom channel and the two in the end caps where they exit look OK.
Thanks in advance.

[GMH]

OK...problem solved! It would only raise about 8" and then bind. I put a tiny drop of Tri-lube with Teflon on all of the bushings in the bottom channel and it opens and closes like a dream now! In all the videos I watched and forum posts I read, I never heard anyone recommend lubricating them.

[wingnut60]

Well, glad you found it the hard way, 'cause probably none of us have ever lubed one of the bushings. My wife restrung many of these, and even the large rear one, and they never got in a bind.