I have a Japanese 15 clone that I bought at a thrift shop for $5!!! I was amazed at how well it sewed--great stitch. I made a quilt with it and decided that it was my favorite machine of all. Suddenly the upper tension would not release or adjust. I disassembled the tension and cleaned it. When I put it back together it worked okay for a little while. Then back to no release even when I raised the presser foot. Any suggestions? Should I be using something other than sewing machine oil to clean the tension assembly parts? Thanks in advance for any help you can give me. I really want to get this back to working like it was.