keyboard suddenly fails

Version: Build ID: 420m0(Build:2) on Ubuntu 14.04
New problem after many years trouble-free: After a while working in Writer or Calc Libreoffice fails to respond to ANY keyboard input but keyboard ok in other programs [eg I am typing this!]
I changed keyboards, same problem.

What’s up doc?

Unlikely anyone is going to try to troubleshoot such an old version.
I suggest you update to the current stable version 5.4.
That may solve your issue.

Thanks, understood.
It looks like I’ll be forced to take something Ubuntu doesn’t recommend. [checking on Synaptic it shows 0ubuntu5.3 as BOTH the installed AND the latest version].
I am most reluctant to risk many hours of wasted time by taking something not ‘authenticated’ by Ubuntu like I had with the disastrous bugs in 4.2.6&7.