Yes, mine too except when the progress bar appears. Then the extra two (?) pixels cause everything to the right to shift over and back again when it disappears. The bar doesn’t show up for every folder.
I’m guessing there’s a lower duration threshold below which it’s not displayed. I presume if you find a large folder (many files, preferably not yet read) it would show up.
At least that’s what happens on my system.
I thought it showed up in my gif. Maybe it didn’t play for you.
And, Isn’t it actually always visible, also in its 0% state?
OK, that’s weird. And yes, it’s visible only when >0.
I wonder if there’s a stray .gtkrc (or similar) somewhere that’s influencing mine. But it’s Windows, so that’s less straightforward. Are you on Win 10 or 11? Might be a GTK difference between the two.
At any rate, it’s certainly not a show-stopper, I just noticed it with the pre-release zip version Alberto made available. I’ve not upgraded to the latest and will do that ASAP. It’s clearly visible when it happens, but functionally inconsequential.
Your GIF works. I just looked and didn’t click. 
W11.
Gifs have allways autoplayed for me. Good to know that it’s not standard everywhere. 
I’ve never noticed this, but I must admit it’s the kind of thing to which I normally would not pay attention, so I can’t be sure it never happened… That said, it’s probably something that can be fixed in the theme CSS. If somebody wants to give this a try, I’ll be happy to accept the contribution 
Well I would’ve never noticed it except it makes the entire thumbnail pane jiggle briefly right then left. But it’s not happening to @apostel338 so it’s apparently something on my system (I guess?) that’s making the progress bar ~2 pixels too wide. Maybe it’s gained a little weight after the holidays…
Then again, I didn’t lose any sleep last night, so… 