[Sorry if Extensions component is wrong, wasn't sure what to pick]
Running LO 126.96.36.199 on MacOS 10.13.6 in South Africa, where system regional setting uses comma rather than period for decimal separator.
Writer treats strings with period, eg "1.5" as non-numeric and evaluates that as 0. With a comma instead, eg "1,5" the value is one-and-a half. OK, fair enough.
Now I have a macro that extracts a value from a spreadsheet cell, and sets that value into a Writer variable field which is then used elsewhere in a Writer formula.
The latter formula does not compute correctly - result is 0 - because the extracted spreadsheet value (a floating point number, type Variant/Double returned by RangeTLCellValue) gets turned into a string with a period for decimal point in the Writer variable field (DependentTextField.Content = myNumericValue)
Either the implicit double-to-string conversion should be using the same punctuation that's expected elsewhere (so comma not period) or else everything should accept a period as decimal separator in number strings, and then do the local-dependent presentation only at the formatting stage (which is what OpenOffice used to do: this macro began life there).
FWIW I tried changing Language settings in the document, made no difference. Presumably the system locale trumps that for number parsing. This also affected static "set variable" fields in the template: I had to change decimal periods to commas in those too, to make the formulas work.