Every time results are coming differently for docking of RNA with a small molecule. Also, interaction reduces when energy minimization has been done(Avogrado, Chem 3D, Chem 3D ultra)
for RNA, I would suggest using HADDOCK or other tools which are more optimized for docking RNA. The atomic constraints used in autodock are not optimized for RNA ligand docking, that is why there is variability in results.