[Issue]: Updating to 1.21.10 from older versions causes game to crash

[TheMCNerd2017]

What is the issue?

Version 25.19.16-fabric-1.21.10 of the modpack fails to launch in PrismLauncher, resulting in a game crash almost instantly due to a ModernFix mixin failing.

To Reproduce

1. With PrismLauncher, update the modpack in an instance to RC 25.19.16 (fabric) -- 25.19.16-fabric-1.21.10 from Modrinth.
2. Launch the modpack in the instance that you just updated.

Minecraft Version

1.21.10

Modpack

Re-Console Modrinth

Log and crash report

Re-Console Modpack crashed. The logs have been uploaded to gnomebot.dev:

latest.log | crash-2025-12-13_11.59.33-client.txt | crash_assistant_app.log | modlist.txt | i9-13950hx might be the reason for the crash

Mod list changes on top of the modpack:

�[2;32m11�[0m added, �[2;31m10�[0m removed, �[2;34m31�[0m updated.

Additional Context

RC 25.19.16 (fabric) -- 25.19.16-fabric-1.21.8 works perfectly fine, this almost instant crash is only occurring on the 1.21.10 edition of the latest fabric version of the modpack. It appears the crash is being caused by a mixin transformation from ModernFix failing.
The crash assistant also showed an extra dialog about my CPU being vulnerable to the Intel CPU degradation issue and automatically put an extra link to an article about it next to the auto-collected logs. I confirmed that the CPU was not the cause of the crash. Additionally, the cause of the crash is the exact same every time.

Acknowledgement

• I understand and have fully filled out the form, including the issue name.

[forkiesassds]

This issue happens when ONLY updating an existing Re-Console instance to 1.21.10, new instances are fine. The issue isn't caused by us, but rather by a maintainer of a mod we rely on seemingly being too lazy to properly fix a feature which had been enabled by default in previous versions.

The following will solve the crashing:

1. Open your instance's .minecraft folder.
2. Navigate to the config folder.
3. Open the modernfix-mixins.properties file
4. Scroll all the way to the bottom until you see a line along the lines of mixin.perf.dynamic_resources=true
5. Replace the true in the line with false, or remove it entirely
6. The game should be launching again

[TheMCNerd2017]

This issue happens when ONLY updating an existing Re-Console instance to 1.21.10, new instances are fine. The issue isn't caused by us, but rather by a maintainer of a mod we rely on seemingly being too lazy to properly fix a feature which had been enabled by default in previous versions.

The following will solve the crashing:

1. Open your instance's `.minecraft` folder.

2. Navigate to the `config` folder.

3. Open the `modernfix-mixins.properties` file

4. Scroll all the way to the bottom until you see a line along the lines of `mixin.perf.dynamic_resources=true`

5. Replace the true in the line with false, or remove it entirely

6. The game should be launching again

That fixed it, thanks! Though I'll probably stick to 1.21.8 though until the 1.21.10 version has more of the mods present (like the custom player models). Should I close this issue?

[forkiesassds]

I'm keeping it opened and pinned for anyone in the future who might encounter this issue.