The Sign Change button +/- seems to be buggy. If I enter a number, and click the +/- button, the sign changes to (-) but if I click again, the result is very odd.
Example: If I enter 34 then click the +/- button, the result is -34, which is correct; but if I click again, I would expect the sign to toggle, leaving 34. But instead, I get -4.4.
Also, the results are bizarre if I attempt to change the sign after a chain of calculations.