Why is Ubuntu 14.04 64 bit LibreOffice 5.0.3.2 unstable?

Seems as if it may be related to video card/driver

If the OpenGL-related suggestions in the linked answer prove ineffective, do try upgrading the system video driver. Also note that Ubuntu 14.04 is old and certain system components may be incompatible with LO v5.0 (from memory v5.1 is incompatible with this version of Ubuntu). It is simply too old.

For god’s sake @oweng, you’re telling to ditch an LTS release in favor of non-LTS.

… or use an older LO release, such as the one that is compatible with that LTS. There were no details provided in the Q about how the LO package was installed or from what source.

Can be possibly the OpenGL bug; see reply to Q64314. There is also a current GTK3 issue, but I cannot find the link for that.

Generally true, but with PPA variants instability can also be due to packaging / changes by distribution developers. It is more difficult to determine problems for PPA variants for this reason. List of “gtk3” changes here and “gtk” bugs here.