Apparently this was an issue reported November 2015 for Windows. I’ve just installed above LibreOffice on Linux Mint Mate desktop and get the same problem. Not sure why it was not fixed in the ensuing period? It’s a serious UI bug that detracts from the usability of LibreOffice. I was using an older version until now and never had this problem. Installed a new PC with current LibreOffice and bang, this problem appears. I would’ve thought the program got better with age, not worse.
Using LibreOffice Calc 25.8.0.4 and Linux Mint Mate 22
And sorry, I can’t revert to a previous version which is 4 years old, or test every single release since then to check if this bug is fixed.