Zooming in the PDF viewer does not stick. The page scales for a moment
and then snaps straight back to the previous size, so there is no way to
settle on a zoom level.
macOS 26.5.2, Chrome. Happens on every PDF I have opened.
Happy to help track it down: I can send a screen recording, test a fix,
or give you details from any specific file that reproduces it.
Could you take a look?