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Sorry that I did not respond the same day. I did not get a notification about your response. 
I checked the book a couple of times when I was thinking how to solve the puzzles. I just cut these moments because I do not talk there at all. The bug must be because of my resolution. My native resolution is  3840 x 2160 so some UI elements may get lost. To fix it I would suggest many ways:

You can anchor UI elements to its borders or get the UNITY AUTOMATIC UI ANCHORING plugin to fix UI problems.

Additionally, Unity has an option to let people choose the resolution before starting. It has to be somewhere in the project management section, so I would prefer the resolution you planned players to use. To test UI scaling, you can change aspect ratios during the play mode in the Unity Editor.

I personally use this C# code to fix my anchors through the code:

rectTransform = objectDragInstance.GetComponent<RectTransform>(); RectTransform parentRectTransform = null; if (rectTransform.transform.parent) parentRectTransform = rectTransform.transform.parent.GetComponent<RectTransform>(); if (!parentRectTransform) return; Undo.RecordObject(rectTransform, "Anchor UI Object"); Rect parentRect = parentRectTransform.rect; rectTransform.anchorMin = new Vector2(rectTransform.anchorMin.x + (rectTransform.offsetMin.x / parentRect.width), rectTransform.anchorMin.y + (rectTransform.offsetMin.y / parentRect.height)); rectTransform.anchorMax = new Vector2(rectTransform.anchorMax.x + (rectTransform.offsetMax.x / parentRect.width), rectTransform.anchorMax.y + (rectTransform.offsetMax.y / parentRect.height)); rectTransform.offsetMin = Vector2.zero; rectTransform.offsetMax = Vector2.zero; rectTransform.pivot = new Vector2(0.5f, 0.5f); rectTransform.pivot = new Vector2(0.5f, 0.5f);