The validation in the numeric text boxes is a little buggy. In an attempt to prevent invalid characters from being entered, the code was written so that any text you enter into the text box will automatically be converted to a number, and then the number is used to repopulate the text box. This causes the number to be reformatted, so that leading zeros before the decimal and trailing zeros after the decimal get stripped. This also removes the decimal if there are no significant digits after it.
The workaround is pretty simple, though. Let's say your latitude is
34.898064. First, enter
34898064 into the text box, then insert the decimal in the appropriate spot.