Calibre footnote viewer missing out words

I noticed a curious thing inspecting footnotes in the footnotes panel. Some words are missed out, usually book titles done with a span class italic. The missing words are still missing when the footnote panel is undocked. But when the footnote is viewed in the main view the missing words are back and everything is fine. The EPUB validates and there is nothing wrong with the code at these points. The problem is also sporadic, not consistent. Similar text might be displayed fine.

Is this a known issue? I wish I had a Kindle Paperwhite to see whether it also happened there.

Edit: This is in v 2.52.