The biggest impact on the level being out on an instrument or back site is the plump line to the mark, you will not impact a forced cantered traverse, but your independent setup on the same marks will immediately show any error in the plump site being off because the tribrach wasn't level. This is because the 0.001mm error will be around 10 times higher when you project the error 1.5m down to the mark.
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The biggest impact on the level being out on an instrument or back site is the plump line to the mark, you will not impact a forced cantered traverse, but your independent setup on the same marks will immediately show any error in the plump site being off because the tribrach wasn't level. This is because the 0.001mm error will be around 10 times higher when you project the error 1.5m down to the mark.