pdf export not working

I can no longer export pdf files. It goes through all the motions but with no result.
Export as pdf. Press OK. Choose destination
What happened?
Using version 6.0.7.3
Just upgraded to 6.1.5.2. No change.
I am running OS 10.13.6 on a 2012 27" iMac
Saving to desktop. Used to work until this week.

Now I get a pdf that just is pages and pages with the lines
_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F
_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F
_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F
_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F_x005F

Which OS do you use? Describe the steps of your approach. Where do you store

Complete your question by editing.

I am on an even older iMac (late 2009) also running OS 10.13.6. LO 6.1.5.2

I just created a simple Writer doc and exported to PDF and it worked fine. Did the same with a Calc file. No problems at all. Try quitting LO and restarting your computer maybe.