Biscuit jointer miter alignment problem

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The Grandmother clock is my current project.
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I want to join the trim pieces using the SS Biscuit Jointer.
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But this is the result of a test on a scrap piece of wood.
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The problem appearers to me to be excessive slop in the guide rods as they slide in the housing boss making the entry angle of the cutter blade unpredictable. My question is; has anyone encountered this problem and how did you overcome it.
My thought is to make a sled that would slide under the biscuit jointer housing with an adjustable 45 deg extension to clamp the piece to be mitered. This would enable fine tuning of the entry angle independent of the biscuit jointer guide.