A few signs of a slow plex install can be
- Loading the dashboard results in "An unexpected error occured loading the dashboard
- Loading a library results in "An unexpected error occured loading this library
- Some posters on movies or TV shows are now showing a trash icon
- Loading a library takes a long time
These issues can be resolved by running plex maintenance tasks, such as empty trash, clean bundles and optimizing the database.
In order to run these tasks, refer to this screenshot - Run them in the same order as presented on the arrows