Please test using the latest Hydrus release to make sure your issue has not already been fixed. When you open an issue for older versions than the current one you might get told to update to the latest version first.
If you are having issues with lag, please check this article first before opening an issue: https://hydrusnetwork.github.io/hydrus/help/reducing_lag.html
Hydrus version: please also state if you are running Hydrus via executable or from source. If you don't know what that means, you are very likely running via executable. If you are running from source, please include details on how (e.g., installed dependencies via pip, installed the AUR version etc.)