does not have the unique extendability property as possessed by the constraints considered here. And it seems to be a major open problem to get the precise threshold for constraints without unique extendibility and not similar to $2-$CNF. A mere existence result is the Friedgut-Bourgain theorem [@FRI]. Based on this theorem thresholds for formulas of constraints over domains with more than $2$ elements are considered in [@MO]. Ordering constraints are considered in [@GO], only partial results towards a threshold can be proven. In order to get definite threshold results further techniques are required. Therefore it is a useful effort to further develop the techniques with which thresholds can be proven. This is the general contribution of this paper.

A notable early exception, in that the precise threshold can be proven is the $\mod 2-$case considered above. Historically [@DUMA] is the first paper which uses variance calculation based on Laplace method in this area. Subsequently, for $k-$CNF SAT this method has lead to substantial progress in [@ACMO]. The contribution here is that $\mod 2-$proof can be refined and extended to cover other cases based on observations of independent interest. Note that random sparse linear systems over finite fields are used to 