I have been having the same issue using the past three versions of Adobe illustrator this also happens in macOS sequoia and in macOS Tahoe. When I create a new document and I choose the size for the document, I have to enter the dimensions three times before it will accept them. Each time I enter a dimension in one of the fields and tab to the next field it will automatically revert back to the old dimension that was there and I must do this three times in a row before it will finally stick and accept the dimensions I’m entering. This has been a repeating issue for a very long time and I sincerely wish Adobe would fix this. I have spoken with a tech concerning this. I have completely uninstalled the Creative Cloud suite and reinstalled with no change. I have removed preferences, application support files, created a new user account and nothing seems to help
I am currently running the newest version of macOS Tahoe and the newest version of Adobe illustrator but this has been happening for at least the last three versions of Illustrator and it has been happening in Sequoia before I upgraded to Tahoe and it’s not intermittent. It happens every single time I created document. This is so frustrating. And what is more frustrating is that after speaking with an Adobe technician and spending an in inordinate amount of time, uninstalling and reinstalling with no solution Adobe doesn’t seem to really care.

Been having this same issue for a good few months now on both mac laptop and Windows PC. Please fix, it's causing major issues and slowing down work.

Have no idea :( Again, I can’t tolerate this new dialog myself.
Thanks for the heads up...

Sorry, I misspoke, it's not the orientation that's the 2nd thing in the tab sequence, it's the unit of measure (inches). As soon as it hits that, it causes the "shift" and it changes the entry in the width field, so I have to go back and change it (there have been times where I have been just going so fast and I don't notice it's done that and I end up with a document that's not the right size and so I have to go back and re-create it).

Yet it doesn't happen every time, which is the mind-boggling part. If it works correctly sometimes, why does it behave incorrectly other times?

It has popped up again. Creating a brand new document, the horizontal (landscape) orientation is selected by default. I enter a dimension for the width (in this case, 25.5 in.), tab down to get to the height field, but as soon as I do that, it has me back in the width field and it has removed my previous entry. It's something to do with when you tab, when it hits the orientation toggle (which is the 2nd thing in the tab sequence, for some reason, instead of going right to the height after the width: width field -> orientation -> height; is there a way to make the orientation not happen until *after* you've tabbed/entered both dimensions?).

At any rate, I may try toggling that legacy option that's been mentioned.

Thank you!

Hi, Egor,

Sorry for my delay. Some busy days at work, and I'm just now having time to reply.

Yes, I think what you're describing is similar to what I was experiencing (the orientation). However, I just installed today's Illustrator update and I am not having same experience (yet), so maybe something was addressed?

I'll give it a few days and see if it pops up again and will respond back as soon as I'm able.

Ah, the flawed modern File > New...
As noted in a comment on forums, toggling it to the legacy one can be a workaround.
I can’t reproduce it, but when I watch the video in the other comment, I notice this happens when the assumed orientation changes, and this makes the buttons for it blink back and forth rapidly — as if Ai tries to swap the values from the height field to the width one and stops in the middle — and it looks as if it restores back the previous value!

Brian, can you make several experiments to see if it’s what it is?
Try to start from a square artboard, but then try the same for an album and a portrait one, and see if behavior changes.