I would like to share a problem I had and resolved in Xenial Lubuntu with LO Calc
Build ID: 1:5.1.3-0ubuntu1 Threads CPU : 4; Version de l’OS :Linux 4.4; UI Render : par défaut.
This problem affects the display of characters when I type. Sometimes characters appear bold or the text is collapsed. When I move to another cell, the text switch to a correct display.
Sometimes it turns correctly few seconds after I stop typing. Sometimes it doesnot
By the way it occurs irregularly.
To solve it, desinstall libreoffice-gnome (1:5.1.3-0ubuntu1) and libreoffice-gtk (1:5.1.3-0ubuntu1); install only libreoffice-gtk3 (1:5.1.3-0ubuntu1).
I hope it would be helpfull for others of you stuck in the same problem.
Have a good one.