LO freezes, easily repeatable problem, anyone know a fix?

I use Ubuntu 18.04, I update almost every day. I have this problem with LO:

Click on LO calc symbol to start LO Calc.
LO calc starts with an empty spreadsheet.
I go to recent files, click on the last one, or any other.

The file does not load. If I wait, the screen darkens. I found, if I click the X to close the window, I get “This window is not responding, do you want to, then 2 buttons Wait Force Quit”

I click Force Quit

Then restart LO calc. It tells me it wants to recover Untitled1.ods After that, I can open any recent file, no problem, but the first time around, if I wait too long, the whole computer freezes.

Also, this does not happen if I first open LO writer.

I recently upgraded to Ubuntu 18.04 from 16.04. In 16.04, this problem never occurred.

Any tips please??

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