I've run those tests and they didn't produce any errors.
I did notice that the tag I'd written with JRMC didn't appear in the tag dump so I opened the file in a biunary editor to check and found this block so it was written to the file.
<?xpacket end="w"?>ÿé Media Jukebox <MJMD>
<Tool_Name>Media Center</Tool_Name>
<Tool_Version>18.0.167</Tool_Version>
<People>Dave & Perri</People>
<Album>12/04/2013</Album>
<Lens>EF70-300mm f/4-5.6 IS USM</Lens>
<Date>41376.5788773148160544</Date>
<Name>Test</Name>
</MJMD>
Craig