Index entries 'randomly' italicised

Since I installed a new version of LibreOffice a month or so ago (details below) index entries seem to have some random italicisation applied, for example:
cosPi 50, 52, 53
decodeBinary 26
decodeDecimal 26
defaultModes 54
I have checked the content.xml and all the source data for the entries above are plain text (single ‘words’), so this looks like a error in the Update All process. How should I report this?

This is the index of the IEEE 754 (floating point) standard and we are getting close to the end of the current revision process so this is fairly urgent.

Many thanks.

Mike Cowlishaw
http://speleotrove.com/mfc/

LibreOffice details:

Version: 5.4.3.2 (x64)

Build ID: 92a7159f7e4af62137622921e809f8546db437e5
CPU threads: 4; OS: Windows 6.1; UI render: default;
Locale: en-GB (en_GB); Calc: group

Can you make available somewhere a sample exhibiting this behaviour? We’ll have a look at it. If you think it is really a bug, report it at https://bugs.documentfoundation.org/