[Bug]: Only the first window can use userchromescripts.

[black-ish]

Pre-Submission Checklist

• I have checked the existing/closed issues to ensure this issue has not already been reported.
• I am using the latest supported version of the browser.
• I have tried disabling all browser extensions/add-ons to rule out interference from these.
• I have tried clearing the browser cache and cookies.
• I have checked with a new profile and the issue still occurs.
• I have provided detailed step-by-step instructions on how to reproduce the issue.
• I have included relevant screenshots or console outputs.
• I have checked that this problem is not occurring in the latest version of Firefox ESR.
• This issue is specific to this browser and does not occur in other browsers.

Bug Summary

I had been meaning to implement proper mouse gestures and noticed that they work fine in the first(main) window but not in the second or third and so on window.

Things like TabMixPlus seem to work properly it seems.
But anything else only works in the first window but not any other.

Reproduction Steps

1. Download & install Floorp
2. Start Floorp to create a profile
3. Install userChromeJS from here
4. Install mousegestures from here or here, I use the second one and version 127 from it.
5. Use "Clear startup cache…" in about:support
6. Open a second window with Ctrl+N for example
7. Try to use gesture in second window

Expected Behavior

User every gesture fully in all windows.

Actual Behavior

Only the first window has gestures working and any nth window can't use it.

Screenshots

Browser Version

11.19.1

Operating System

Win 10, Win 11

Additional Context

I have no idea how to even begin debugging it as I'm not a dev in any way. There seems to be no console output of any kind.
Things like extensions (Gesturify) work but they insert js into websites so the gestures are limited to those and when they are loaded, which is why I'd like the userchromeJS solution to work and as well as other scripts I might potentialy add later.

I opened the same issue {here}(xiaoxiaoflood/firefox-scripts#319)