Preview app problem in Big Sur

You are not alone OP.

Bear in mind that this issue ONLY occurs when you have more than 1 pdf open in Preview (at least on my side, usually when I open a single PDF and go fullscreen it doesn't show the annoying "slideshow" square).

This is definitely a bug, and one that should be fixed ASAP.

Being someone who is all the time working with many PDFs, I'm seriously considering rolling back to Catalina.

My MacBook Pro 15" (2016) is having the same issue and it is very frustrating. It looks to be a simple bug so hopefully it will get fixed soon.

I also reported the problem via the macOS feedback page here:

https://www.apple.com/feedback/macos.html

Until it is fixed, the workaround is to only have one PDF open at a time, when working in full screen.....☹️

don't bother Big Sur is not better than Catalina at all, its worse, I'm having the same problem

plus when I'm swiping between windows its so glitchy and choppy, I'm really frustrated using this OS

they improved it to the worse :((

I have the same problem, it's horrible and it only brings problems.

When in full screen mode that black block shows up and slows down switching between windows. Furthermore, as I have already said in another post, when in full screen with multiple panels, Preview just keeps switching between tabs for no reason.

It's frustrating.

For some reason, I cannot successfully edit my post...

Correction: Issue also happens when I have only 1 PDF open.

It seems if you open only 1 file in full screen and do not switch to other apps, it won't come. But as soon as you leave Preview and come back, there it is...

its so frustrating till this day, I dislike Big Sur so much I can't get work done, problems with Preview showing me a play, forward, backwards buttons when I'm working on a pdf *facepalm* , its choppy very laggy animations

(I'm using nearly fully specced 16 inch MacBook Pro, that was blazing fast in Catalina) now its all gone bad because macOS just makes you want to get work done, now I hate to do anything from using safari that uses 1.5GB for Gmail to previewing PDFs

I just bump into a new problem or get frustrated with the very laggy animations

Since I updated to Big Sur anything I download whether jpeg, jpg, PDF, HEIC or png, comes without a preview. Finder says that the picture is previewed. Any attempt to obtain a preview has failed.

FWIW, "Command Shift F" switches to Full Screen, "Control Command F" switches to Slideshow. I don't get the "player" unless I switch to "Slideshow".

You're welcome. I don't know what the cause would be. I have three Macs running Big Sur and none behave as you describe.

You're welcome.

It is the other way around.