I find the same thing. It usually when i get to a few pages in depth with Components on each page.

They fixed it once before and now it seems to be creeping back, although not as bad as before yet. And I get a lot of container elements jumping about out of position quite often too.

I have a pretty fast PC (i7-8700K, 32Gb, NVM SSD), but even on startup, Site Designer (V5 latest build) is pretty slow. It takes about 15 seconds to startup, and then I have to load my actual project which takes another five or six seconds.

I haven't noticed it getting any worse after a Windows 10 update though.

You
Should try it on windows11 I can have my breakfast before it's fully loaded about 30 pages, with quite a few images and some fancy stuff going on, not too bad now for starting a new project.
I disabled the error log file thingy and it seemed to help especially when a project has been open for a while

Just curious how large is your project and how many Symbols do you have on your project.

I have noticed this issue as well but usually only on my larger projects that have a tonne of Symbols.