Impress - running show non-stop

I am setting up a Raspberry Pi to drive a shop display. I find two (not major) issues:

a. Though the PowerPoint file is configured to run indefinitely, there is a black screen pause of 10 seconds when it reaches the end of the show. There is a count down clock on the top left. When it reaches 0, the last slide is made visible again before it transitions to the first slide. Is there a way to remove the count down pause?

b. For Microsoft pptx files, the continuous looping won’t work. When it reaches the last slide, it requires a user click to continue. Is there a way to overcome this? The same file runs fine if saved in ppt format.


LibreOffice (Build ID: 360m1(Build:2))

I would try to change the time in
SlideShow > Slide Show Settings > Type: Auto and change the time below

This is an unattended computer that has everything loaded automatically. I can’t change things that are specific to a file. I can only change global LibreOffice settings. Is there a way to pass these settings on the command line when launching soffice?