On my Gnome Fedora 30 machine, I have problems with the impress Previous Slide function.
In presentation mode, when I hit PageUp or Left Arrow, it usually does not go back. It changes to a different slide, but it’s not the previous slide. It usually keeps going forward.
Actually even that’s not certain. I went to the second slide of a document and PageUp brought me to the first page.
I then went forward a few slides, tried to go back, but it would not work. It kept going forward!