Multiple pages gives error while loading

Since a couple of weeks I can’t properly access home assistant anymore from my pc.
First of all it looks a bit weird, for example the menu items Config and Developer Tools are written instead like config and developer_tools. When I click on the menu items, it just shows: ‘Error while loading page config’.
I’ve tried restarting home assistant, my pc, clearing cache etc, but it keeps happening. It happens in both Chrome and Edge. However, on my phone and MacBook I can still access everything just fine. Does anyone know what I could do to solve this?

Some info:
Installation Type: Home Assistant Supervised
Version: core-2021.3.0