Question: Can parameters "get lost" in some solutions?

I am re-posting. I am not sure why my question was deleted. Please advise on how to amend my post so that it's not considered spam.

I simply wonder how parameters can "disappear" in a solution. In particular, in my example below the parameter gamma correctly appears in 3 out of 4 solution. However, the solution in which 'gamma' does not appear is also the solution I am most interested in, given its manageable size. Why gamma is "lost" for this solution?

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