Charts get written to all sheets when reloading

[luke-quadratic]

(created separate from #911 because this is severe bug)

Charts created in secondary sheets get written to all other sheets when file is reloaded. E.g. if I have 3 sheets and have a chart in sheets 2 or 3, that chart will get shown in all 3 sheets when I reload, and it's shifted away from its anchor.

To recreate: create a second sheet --> create a chart in that second sheet --> reload file --> chart from sheet 2 will be shown to chart 1 and that chart appears to also be shifted away from where it's supposed to be anchored