This is what trying to change a CSS px value in Safari looks like, in case anyone is curious.

Step 1. Find and inspect an element
Step 2. Click on the CSS property you'd like to change
Step 3. *POOF* the entire rule never existed!

Not to defend Safari’s devtools in general (I haven’t used them for months) but I bever had this particular issue - it ”works fine on my machine”

Is it like this all the time for you?

I’m thinking maybe it’s an edge case like if for example some JS is doing updates on the selected DOMElement or similar

@jiraTicket No JS, it happens on plain HTML/CSS pages, but it is intermittent. I haven't been able to figure out what triggers it.

I've been putting up with it for years.