Error is because you need to have same lenght "inside" portal as lenght of "outside" portal. I made small map. Left portal is correct and right portal is incorrect. If you run this map you get displacement error. If you correct lenght of right "inside" portal so portal is same lenght as right "outside" portal, error disappear. In other word situation have to be same as on left map side where portals is correct. Hope that I help you. I know that my description could be little complicated, sorry.
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