It means that either you just need to try other brands of caps or replace your nipples with ones that are precision made like Treso bronze nipples.
You didn't specify what brand cap you are using. There aren't any industry standards for caps. So one brand will vary from another. Even within brands from one production run to the next there will be tolerance differences. I don't like the idea of pinching caps. "In a pinch" it will work but IMHO it isn't the proper or ideal implementation. If they are pinched then they are bowed and that doesn't make for an airtight sealed system. Will people who pinch caps experience an eventual chain fire? I don't know and I don't want to find out. The following pics show my observations on a few different caps I have used.
