I’m experiencing this too, though weirdly enough having a plugin widget visible on screen (although under some conditions, ex. can’t split it with another widget) fixes the issue completely
This is also happening to me. It happened right after the Windows 11 24H2 update. I get around 34 fps.
But, when I enabled next Gen Studio, the lag stopped. Both in studio and playtest. Now, I get 60 fps.
I also get this issue and can also confirm I recently updated to Windows 11 24H2 which sounds like a common potential cause amongst people here.
I will add that in my case, this only happens when the game is not running. Once I press play everything behaves normally after a second or two.
I can also confirm that enabling the next gen studio beta fixes the issue. However, I was not able to get the issue to stop with a floating widget as nakoyasha described.
Thank you for the temporary fix! It seems to have resolved my problem as well. The issue likely began around the time I updated my PC, but I hadn’t considered that as the cause until now.