In Sao branch 5.2, rev 90190d3ab0c3+ when you try to create a tax with a rate value that has potential round off error such as "12.87%", and save the record, then every time you load that tax record (by browsing through the records) the rate field is cleared blank and a the dialog message will popup asking if "you would like to save the record" as if the rate value was modified. This happens only in Sao, and no in Tryton client app.
I am using Mozilla Firefox browser version 69.0 (64 bits) ubuntu linux.
I looked into the Sao code and found that the problem comes from Sao.View.Form.Integer class at the function "get_value:" where there is a call to checkValidity() for the input. It appears that for the float value of 12.87 due to the round off error becomes 12.870000000000001 which fails the checkValidity() call, hence returns NaN.
If I bypass this check, the problem is fixed, but I believe this is not the ideal solution.