Stairs shifted over the winter

[blastra]

I have a new inground vinyl lined pool with 2 sets of fiberglass/plastic steps installed last July. Over the winter(in Maine) it appears that the steps have shifted (both)...one side appears to be 2 -3 inches lower than the other. It is very noticable. The concrete surround cotinues to be level. My primary question is, can this be fixed easily? And is this due to frost or a defect in istallation, or both?