Calc is breaking my formulas

Since I updated to (on OS x 10.10.5) Calc can’t seem to cope with saving and reopening .xml spreadsheets with very basic formulas.

ie. I entered =B3-B2, and the calculation worked, but when I reopened the file, it had become: of:]=[.B3]-[.B2] which of course was not the answer I was looking for.

It works in .ods but I need .xml compatibility. Should I report this as a bug?

What .xml format are you talking about? Besides, .ods is XML, just that the xml streams are zipped into one container.

Oh, it must be the awkward Excel 2003 XML format. Just don’t use it.