I've seen this issue on a couple of build now. Both times the cause was the WeltPixel GTM module.It's worth disabling that if you use it to see if that works for you.
I am soon after returning to 2.3.3, on the grounds that when I introduced 2.3.4, I discovered I could at this point don't sign in the front end or add items to the truck.
We also fetch the same issue on my development site. after upgrade 2.3.4 when I open the category list page display all products or when I open second-page use pagination link. second-page display the same products. I think Magento gets the wrong collection.