In AOO 4.1.2 on Windows 10, I opened Formula (OpenOffice Math) and entered the code directly into it. I see the same problem with the capital Pi and centering of the above and below items. (The Pi looks left aligned rather than centered beneath the over/under rows.)
This isolates more to be looked at in the saved document.
An amusing aspect of this for ODF-wonks is the use of the settings.xml file for something that is not quite what the intended purpose of that is. Since settings.xml is implementation specific (and documented who-knows-where for OpenOffice.org).
Here are some more results:
For the *.odf (Formula) file on Windows 10, both Apache OpenOffice 4.1.2 and LibreOffice 5.0 show the same defect.
For the *.odt (Text) file on Windows 10, both Apache OpenOffice 4.1.2 and LibreOffice 5.0 show the same defect. Microsoft Office Word shows the product notation entirely as expected; there is extra space between the product symbol and the "x + 5". I can't tell if that is showing where something is expected in the Equation Design or it is an actual space. It may be that the {x + 5} is needed in the OpenOffice Math entry. Something to check.