Double Hung Windows Won't Stay Open

A contractor from 14141 says:
I'm working on a large home. It has a pending sale. Upon a home inspection, the report came back that the double hung windows won't stay open. There are about 50 windows affective. They are a custom window. I have spent 3 hours looking for manufactures marking, none found. Please help. If I can't find parts tp repair, is there any after market slide & balancers that can be installed. I have pictures of the existing slides and balances.
Thumbnail of the uploaded file named PHR22420.jpg
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Bob from SWISCO responded:

Thanks for posting. This looks like our 15-104 Caradco Friction Shoe. However, if the springs themselves are broken, then I'm afraid we can't replace them. This is because this shoe is used with a jambliner system, where the springs are part of the jambliners themselves. If they are wood windows, contact your nearest millwork, and they should be able to supply what you need. Best of luck with your repairs.

A contractor from 14141 says:
Thank you for the quick reply.
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