Thanks for your reply.
That is in fact what I did initially, but I found that the Debian maintainers were not happy with me submitting bugs for a non-Debian OS, even though I pointed out that Sparky was fully compatible with and based on Debian testing Stretch. In this case, with the dodgy Libreoffice 5.1.5~rc1-1, I ended up submitting the bug on bugzilla straight to Libreoffice. I noticed today (Friday 05th August 2016) when I did my system update, that Libreoffice was upraded to 5.1.5~rc2-1, but the bug is still there. Thus, I ended up purging my system of Libreoffice, and downgrading to 184.108.40.206-2, which works perfectly.