PropertiesChunk.writeProperties: ASCII_STRING properties must be written as ASCII_STRING properties but not UNICODE_STRING as written raw value (PropertyValue.getRawValue) is formatted as ASCII_STRING. Without this fix writing a MSG with ASCII strings causes the strings to be written with UNICODE type information but ASCII string content which causes the ASCII strings interpreted as UNICODE when re-opened. See https://github.com/apache/poi/pull/146
Change looks ok to me - but it would be good if someone who knows more about the old H**F formats could also review this.