These were not very good strainers to begin with, & it's important that all parts are tight & move parallel to each other. The slightest bit of looseness will prevent the proper action. If you inspect it carefully, you might be able to spy a place where where a c clamp washer , or wound thread can be inserted to return the action to parallel. Even frequent lubrication can help. In the meantime, you might start fishing the internet for a functional strainer.