How to interpret Mendelian randomization results?
It looks like you have linkage as opposed to linkage disequilibrium, therefore horizontal pleiotropy is an explanation of the calculation. 

The calculation appears to be a GLMM around the beta distribution, the residual looks low (which is good). The heterogeneity statistic is significant, you would need to assess whether this is an index of heterozygosity, but it will relate to expectation of Mendellian inhertiance based around the Hardy Weinberg equilibrium.