**EDIT: Now realised that this is because when the symbol first opens in the Sch LIB editor, the grid is displayed at half the resolution: **
Just been editing some existing symbols and found origin was not at centre of symbols so tried to correct using:
**Set origin to centre grid of symbol**
Found that this did not work at 100% zoom. Worked OK if I set zoom to > 100%.
**This appears to be because when the symbol first opens in the Sch LIB editor, the grid is displayed at half the resolution: **
but if the zoom is changed, even if it is then set back to 100%, the grid resolution doubles:
