By far the most common cause of UI slowdowns I saw with SageMaker Studio Classic was when working inside local git repository folders with a very large number of active changes: An unfortunate interaction between the open-source JupyterLab-Git extension (which frequently polls the git changed file list) and EFS' latency characteristics (per-file network traffic, rather than a block store like EBS) - meant that if 1) you had thousands+ of changed/added files that weren't gitignored, and 2) you navigated to any folder within the scope of that git repository - the UI could get super slow. For example I saw one GitHub sample that created 30,000+ tiny JPEG files from MNIST data and didn't .gitignore them. Ouch!

In this particular case, my usual solution was to navigate to any folder outside the affected git repo (to un-block the UI), then use the terminal to add a .gitignore for the relevant files in the repository.

However, that problem's usually pretty instantaneous unless you have something gradually creating lots of extra files. My only other suggestion would be if maybe you're using some custom JupyterLab extension?

I did note you said the kernel was becoming unresponsive, but "the page just infinitely loads and then sometimes gives a connection error" made it sound more like a JupyterServer issue? If it really is the Kernel Gateway app that's bogging down, then 1) it shouldn't be affecting your JupyterLab UI much - just the kernel itself being very slow to respond to requests or not connecting. and 2) Do check that you're running your htop/etc checks on an image terminal and not a system terminal?