I use QGIS 3.16 to visualise a layer of the countries of the world. The layer is saved with the WGS84 CRS (EPSG:4326). I have set all my labels through rule-based labeling and saved the coordinates of the said labels in my shp layer.
However, I do not want this countries layer to be saved using WGS84 but World_Mercator (EPSG:54004). So, I have tried to export my layer and tell QGIS to use World_Mercator. But, when I copy and paste the style from the layer in WGS84 to the one in Mercator, something goes wrong.
All of my labels are relocated to the point (0,0) on my map - in the Gulf of Guinea - but still linked to their stored position with a line.
I thought it could be a problem about the way coordinates are stored. It did not make much sense but I translated all the labels coordinates in Mercator and tried to repeat the operation. It did not work, the same problem happens again.
I would not like to make something like "rebuilding" my shape's labels nor use a dots system with the labels positions, which would be not really "pleasant".