Channel Balances do not click into place and stay attached to window

I have two problems with the channel balances on my Seal Craft windows.

1. Some of the balances do not stick with the window. They either stay in one place or move up and down the track some but not in sync with the window. Is there some way that they are supposed to click into the window itself? Can you give me any advise on this issue?

2. I will need to replace many (all?) of them as the old ones no loner work. They are 10 years old and some cords have broken, some parts have rusted tight, and on some the little clip on the end of the cord that attaches the bottom of the channel balance to the window frame has broken. I know this much:
- Here are some markings I found on the existing channel balances: 29-5[or S?] CA2 CMC 4 and 29-6 HA2 CMC 25.
- They seem to match your series 350. The top plastic insert has not ears. The bottom plastic insert does have ears.
- There are two size windows weight of the smaller ones is 24 to 25 pounds so that would seem to indicate the 2940 in the 350 series. I have not been able to weigh the larger window yet.
- I'll need 20 of the lower weight ones. And 6 of the higher weight ones.
- The spec sheets we have from the architect seem to indicate that they are Seal Craft 4000 series windows but there are no markings on the Windows themselves to confirm this. In other words, we cannot be 100% sure that the contractor installed exactly what was specified but they do seem to be the same.