Resource reload failed

Hi, I'm a player on a minecraft roleplay server and we've been using Iris for a long time. For some time now, several of our players have had a problem. When they connect to the server, the texture pack doesn't load and the following message appears (see screen), some of them even find themselves sent straight back to the minecraft selection menu. The Devs and I think it's a problem because our texture pack contains CITs that can create this bug. That's it, I can provide a list of my mods, logs and such if needed. Have a great evening. Translated with DeepL.com (free version)