Bug Multiclipboard makes N++ close.
I have Version 8.5 32-bit and whenever I select a lot of text, With “Auto copy text selection” on then the app will close.
MultiClipboard isn’t a plugin that you can see in the Plugin Admin list, so cannot select and install it. It is likely (given it seems last version was 2011 according to GitHub) that it’s incompatible with the recent versions of Notepad++.
How about reading the FAQ post here and follow the instructions for running without the plugin.