If it's cast next to/near stairs, slanted walls, slopes or weirdly-formed rocks the rift apparently can go below the surface or sky-high. It's a bug that has been around since the new moving/dynamic rift was introduced, afaik it happens more easily in some places rather than others. And, this is just my personal intuition speaking, that probably was the reason the rift was static beforehand; the devs back then, when Destiny 2 was under development, must have realized that the engine runs into problems with dynamic rifts early on, but since those devs must have left Bungie (or are working 24/7 on Marathon) the current ones were unaware of it and just went along with making the rifts dynamic.