Headers disappearing, scrolling broken

[Celeste5D11]

I have a 339 page book that has elements disappearing - headers on several pages, and when I get part of the way through the document with scrolling it starts to scroll backwards and end up in random places. This is not a huge document-- just text and one image, it has no forms or anything fancy. The headers were still gone when I closed and reopened. This happened at the same time that it said it no longer could find a certain font.
It seems like the program is getting overloaded, but it is altering my files at the same time.
I turned off other programs, updated Adobe Acrobat, restarted the computer, and it happened even worse. I even got a whole new computer and re-installed everything a few months ago.

[Celeste5D11]

I tried adding the headers back in to the pages where they were missing, and it added headers to some, but not all of them!

[Juand5D59]

I am finding a similar issue - I have a largish file thanks to images but only 60 pages - as I make changes adding and subtracting pages I also get the message about the font and it says it will replace the letters it does not recognise (always the same ones) with full stops - which it does not. So I cannot even edit the information back into the file. This is costing me hours of time. I have plenty of RAM and am running an AMD Ryzen chip to handle the graphics so I doubt it is machine related - it is always the same words affected so I suspect there is a glitch in your OCR software somewhere. I can supply images of the pages.

[Dave__M]

It might be a useful experiment to try opening this PDF on another computer if you have one at hand, and check if the issue happens there.  Does this occur with only this PDF, or have you experienced it with others on the same computer?  Any further details you can provide could be helpful in troubleshooting this.

My best,

Dave