Last week I did some casting with my new RCBS mould. Once the mould got to the right temp everything went great, and I cast about 200 bullets. Yesterday I did some more casting. I found that the bolt that the sprue plate pivots on kept loosening up. I had to tighten the bolt after every 6-8 pours into the mould. The bolt has the flex washer under it that it came with from the factory. What else can I do to keep this bolt from loosening up while using the mould?