small freezes when using multiple keyboards

[SpideR]

I'm using 2 keyboards for gaming * and when i press a key on one of them, then press a key on the other (which happends some times per second, it's not rare at all) the game freezes a bit, something like 100ms i guess. It's really incapaciting, i can't use XFCE as my daily DE because of this bug

I'm pretty sure this bug comes from XFWM, because when i change my WM (openbox --replace, for exemple), the bug is gone

During my searches about this bug, i found one on Gnome which exactly looks like the one i'm describing : https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/1858
It looks like a poor response to MappingNotify event (which indeed happends each time i have the freeze, when i press/release a key on a keyboard which is not the last keyboard which i pressed/released a key)

* I don't really use 2 keyboards, but my mouse (Logitech G502), like many mouses with configurable additionnal buttons, is detected as a keyboard by the system, so nearly everytime i press on a mouse button, this bug happends

Description: Ubuntu 20.04.2 LTS
Release: 20.04

xfwm4:
  Installé : 4.14.1-0ubuntu1
  Candidat : 4.14.1-0ubuntu1
 Table de version :
 *** 4.14.1-0ubuntu1 500
        500 http://fr.archive.ubuntu.com/ubuntu focal/universe amd64 Packages
        100 /var/lib/dpkg/status

I expected no freeze when i use my keyboard or mouse

Instead, each time i use my keyboard or mouse, my computer has a small freeze

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xfwm4 4.14.1-0ubuntu1
ProcVersionSignature: Ubuntu 5.8.0-45.51~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-45-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: XFCE
Date: Thu Apr 1 13:30:45 2021
InstallationDate: Installed on 2021-03-10 (21 days ago)
InstallationMedia: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
ProcEnviron:
 LANGUAGE=fr_FR
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 SHELL=/bin/zsh
SourcePackage: xfwm4
UpgradeStatus: No upgrade log present (probably fresh install)