Why all the items in the Canvas reseting the coordinate Y?

Perhaps bad anchoring or layout?

Here are some notes on UI Anchoring, Scaling, CanvasScaler, etc:

Usually you need to choose a suitable ScaleMode and MatchMode in the Canvas Scaler and stick with it 100%. Generally if you change those settings you will often need to redo your UI entirely.

I also use this CanvasScalerOrientationDriver utility to make sharing UI for Landscape / Portrait easier. Read what it does carefully.