Polls window cranks

I bought my house in 2000. It was built around 1980 with double glass Pella crank windows. The cranks on my kitchen windows work to a point and then they seem to strip out and lose their catch. I have to get them to latchcl them from the outside using a ladder. That's a real pain. Anothert pain, is replacing the windows. Then I got this brilliant idea to use the Internet and see what I could do.My Internet search limit led me to you. Can you help me? I've included photos. These Pella windows date back to around 1978-80. Any help would be appreciated. Thank you very much