Preview in Tahoe won't open pdfs to full size

I have just downgraded to Tahoe (big mistake).

When I open a pdf in Preview it will open at 79% size by default"

However if I open a pdf with Hide Sidebar as the default, then it will open at 101%:

Once I have opened the pdf with Hide Sidebar as the default, if I then click on Thumbnails it will keep its 101% size:

But when I open a pdf with with Thumbnails as the default view but then click Hide Sidebar, it does not change up to 101% and instead stays at 79%:

I have tried Preview > Settings > pdf > "size on screen equals size on printout", which opens pdfs at 79%. If I change this to "1 point equals 1 screen pixel" it opens pdfs at 88% size.

What I want to do is simply open pdfs at 100% and by default, have them at Scale To Fit Window (so I can increase the window size if needs be.

Oh and FWIW, any time I open a pdf it won't go to the bottom of the screen. It leaves a gap of about 15mm at the bottom.

Any help would be greatly appreciated.