I open a text-only office document. Mac Mojave, 10.14.6 (18G95) on 2018 mbp

I type 'tel'. It is immediately replaced with 'telecommunicationauthorities'. 

Frustrated with this weird behaviour I search preferences and turn off everything that might even removely related to this behaviour. But it keeps exhibiting the behaviour.

I open Help/OpenOffice Help.

I search for autocomplete. It gives me a list of options. but does not show anything.
I press enter and it shows me "General Shortcut Keys in OpenOffice "
Why ? It does not say anything on auto complete it seems. 

To search where 'autocomplete' is I click in that text and type option-F (find)

My text disappears. I get a full white screen. I type "autocomplete" again. It appears in the middle of the screen. I'm puzzled, is this a crash? A new way to handle search? Has my document been deleted or something and replaced with a blank document? Why did my document switch to full screen?

I want to exit full screen mode but it refuses. If I click on the green sphere in top left, it stays full screen. I can not drag anything to resize.
I click on red closewindow button, it asks if I want to save mu changes. ???? No I don't want this, but what about my text, where is it? Can I undo this?
But I don't want to damage my original file either, so I have no choice but to say no.
The screen goes completely black now. Is this a crash? I press quit.
I again get a prompt if I want to save any changes. 

Sorry but this entire behaviour is uncomprehensable and I lost my text due to this. 


So maybe I have two issues here (1) auto-complete not turning off (2) help system crashing. I think the latter is more severe so I report it as that here.