That makes no sense 🤔 The search plugin has nothing to do with themes or skins. Do you have any errors in your logs after you disable the plugin and restart the forum? What about when you run ./nodebb build and restart is everything working after that?
You can hide composer (red button with +) and chat (user avatar as a button) windows by clicking on their respective buttons in the bottom right corner of the screen. Click again to show window and see your own content.
Try to browse forums when composer is opened. This is one more possible action to do.