InDesign Window Size Bug. After full screen preview window resizes alone.

For me, it helped resizing the window to maximum by pulling the handle to the farthest corner. The OS tries to switch to the window's smallest size, after exiting any full screen mode. 

If using an external monitor, go onto System Settings -> Displasy -> Use as Main Display (on the external monitor)

Best I can tell from all the various posts on here - This has to do with the Mac OS since Big Sur.

Monterey, Ventura, M1, Intel, PS, AI, ID all reporting the same behavior.

One question to you both @26807701 @udderball are you connected to an external monitor?

I've seen this behavior when the Mac goes to sleep and when waking up, lags in recognizing the external monitor resolution so the frame ends up in the same exact position each time.

Seehttps://community.adobe.com/t5/photoshop-ecosystem-bugs/p-windows-and-dialogs-shifted-down-on-macos-12-0-1-apple-m1-mac-silicon/idi-p/12552611

Experiencing the same exact issue and it's driving me crazy. I have "Application Frame" turned on FWIW, but as far as I know I've always had it on (unless that's a brand new feature?). This seems to have only become an issue following Ventura update.

MacOs Ventura 13.1

MacBook Pro M1

Do you have Window > Application Frame turned on or off?

What version of InDesign are you running?