A user experienced performance degradation in Core when loading time entries in the Time Card screen. The user already cleared the cookies and cache to resolve the issue, but that didn't help.
You can try to open Core in the incognito mode. If that is working, then that indicates an issue with the browser extensions. If you are using a Chrome browser, you must check the extensions installed on it (More tools > Extensions) and remove the below Rakuten extension from your browser for Core to work properly. This extension was updated recently (update 4.48) on March 19, 2021 and has affected the performance of some websites, including Core.