Two display problems occur when trying to open and read .pptx files.

1)  In file A,  most of the text and some figures show up properly, but on some slide which I believe contain graphs,  the graphs do not display and there is a funny square containing four squares that seems to be an obscure suggestion that some graphic figures or graphs are not being displayed.  
Some web comments suggest the Libre software had this problem but has fixed it.  I would rather not change programs just to read one file.

2) In file B, everything displays, but in one section of slides the font is much much bigger than intended and the text continues most of the way down onto the following page.   There seems to be some significant font size confusion.