LibreOffice now goes momentarily unresponsive with each action

We recently moved from routable (155.100.x.y) to un-routable addresses (10.a.b.c) and now Calc (about all I use) goes grey with each action (enter cell, edit cell, topmenu click). Since everything was fine before the move I suspect the new infrastructure but don’t know what to look for. Any help appreciated.

In what way do you think LibO might be affected by the changes? Do you load LibO from the network? Where is your user profile stored?
V4.2.8 is rather old now. It was released 2014-12-08 (and it never was the most recommendable version).
Related to changes in the network you may have had a crash? Could the user profile be corrupted?

I’m not an expert in networking. To get a useful answer by such an expert you will have to provide more information.