Search box intermittendly freezing

Describe the bug

In Vimium FF, I'm often hitting a problem with the search box, triggered by pressing /. When the problem occurs, the search box accepts one or more search character but then doesn't accept any further input. In this state, if I press further keys, they do not appear in the search box, and they are not searched for. Pressing backspace does not result in the last character being removed. If I press ``/` again in this state, I get the firefox search bar pop up. If I press escape then the vimium search bar is closed.

This problem happens most often after pressing a single search character, but occasionally the freeze happens after 2 or more. Sometimes the search box works correctly, but this is rare. Which behaviour I get is not consistent. It seems to happen across all sites, and it doesn't matter whether the text I am searching for is present in the page or not.

Although this bug is not 100% consistent for me, it's happening very frequently - at least 80% or 90% of the time. I can get a working search bar by repeatedly escaping out of the search and retrying, but it takes many attempts.

To Reproduce

1. Go to URL 'http://github.com/'
2. Press / to start a search
3. Type a few letters

Here's a screenshot - not sure if it's much use.

I'm also having problems with vimium showing white boxes behind a lot of it's UI elements, which you can see in this screenshot. I'm not sure if this is related - I think it's just a display glitch.

Browser and Vimium version

FIrefox 108.0.1
Build ID: 20221219135842
OS: Linux 5.15.85 #1-NixOS SMP Wed Dec 21 16:36:38 UTC 2022
Vimium: 1.64.6

Start by reproducing the issue from the / search entry point in Firefox 108.0.1, then trace Vimium's search-box input handling. Done means the search box consistently accepts typed characters and backspace without freezing or opening Firefox's search bar; no file or test is named in the issue.