You are changing the encoding of a string or array of strings from the system encoding to UTF-8, but the string data value contains characters which are not convertible to UTF-8 because they are not valid in the system encoding. If you choose to change the encoding anyway, any string which cannot be converted will be left in its original byte representation, and may not display correctly as a system string. This issue usually occurs if you open VIs which have been localized in a different language than the language used by your host system. For example, if you open a VI containing Shift JIS-encoded Japanese strings on a host whose system encoding is Windows Latin 1, the Shift JIS text cannot be represented in that encoding and displays incorrectly. If you try to convert that text to UTF-8, LabVIEW will try to convert the text from Windows Latin 1 to UTF-8 and fail to convert since the string is actually in Shift JIS encoding. You may also encounter this issue when trying to convert strings containing controls codes or other binary data. Right-click the string and select "'\' Codes Display" from the shortcut menu to inspect the string data for unexpected content.