<!-- BEFORE YOU OPEN AN ISSUE, PLEASE READ THIS. Hello! Thank you for using Jupyter Notebook. We're glad you're here. Right now, you're opening an issue. Before you do, let's make sure this is the right place to post your question/issue. Jupyter Notebook 6.x development is in maintenance-only mode. Bugs found in Notebook 6.x and that don't reproduce in Notebook 7.x may not get fixed. Work in this repository is focused on Jupyter Notebook 7.x, the former RetroLab project. The code base for Notebook 7.x is very different than Notebook 6.x. If you can, please try reproducing Notebook 6.x bugs with Notebook 7.x using the main branch of this repository. We recommend that you check out JupyterLab (https://github.com/jupyterlab/jupyterlab), Jupyter's next generation Notebook interface. Here, we're looking for specific bugs in the Jupyter Notebook codebase. If you think you've identified such a bug, you can continue opening your issue here. We'd appreciate if you include as much detail as possible, such as links to the offending code, snapshots of the UI issue, code blocks with your console logs, etc. If you're having issues installing Jupyter Notebook, or you're having another issue and don't know how to proceed, try the following: 1. scan the "What to do when things go wrong" (https://jupyter-notebook.readthedocs.io/en/stable/troubleshooting.html#what-to-do-when-things-go-wrong) page in our documentation to see if your question has already been answered 2. post your question on the Jupyter Notebook discourse channel (https://discourse.jupyter.org/c/notebook/31). There are many more people in the Jupyter community that engage on that channel. --> **Describe the bug** While changing any type of size, there is a white screen flashing in Jupyter Notebook v7 **To Reproduce** Steps to reproduce the behavior: 1. Go to 'settings/Theme" 2. Click on 'Increase Code Font Size **Expected behavior** By clicking normally it should increase the size of the font instead of flashing a white screen. **Screenshots** [I Click here for Recording]( https://github.com/jupyter/notebook/assets/106507125/25a8c62f-e4cc-48f8-9869-d8170403b0cb ) **Desktop (please complete the following information):** - OS: Windows 11 Pro - Browser: Chrome - Version: Jupyter Notebook v7 **Additional context** Other Bugs are also there in all the menu bars