LibreImpress: "Loop and repeat after" setting being reset by soffice (6) for pptx presentations

I am trying to use:

soffice --show file.pptx --display :0 --nologo --norestore &

to start a presentation from a bash script.

I have first set the SlideShow settings Presentation Mode to Loop and repeat after 00:00:00.

However, when the presentation gets to the last slide I get the message:

Click to exit presentation...

on the screen. The Loop and repeat setting is ignored.

When I check file.pptx after running soffice, I find that the Presentation Mode is reset to Full Screen.

This does not happen if the file type is ppt.

I have tried setting

Doc.Presentation.IsEndless(true)

in a macro triggered by the OpenDocument event. It doesn’t help.

In any case soffice should not (surely) reset the Presentation mode if it is just displaying the presentation?

I’m using soffice version 6.1.5.2 on a Raspberry Pi

Any suggestions appreciated.