Cannot "sort" elements of layer panel

Im facing same issue

Sorter.ts:500 contains const cv = this.em!.Canvas, which is obviously wrong (as em is null or undefined)

Unfortunately, I don't currently understand the code with all its abbreviations - but: would a change of line 499 to if (model?.set && (this.em != null)) { help here?

Note: indeed, this little "hack" helps me sorting layers - I can move layers down in the list, but not up. And, again, since I do not understand the code, my hack is what it is (a "hack") and not a fix!

Closing as duplicate of https://github.com/GrapesJS/grapesjs/issues/5355

Thanks for reporting this, @rozek.

The error **TypeError: Cannot read properties of undefined (reading 'Canvas') ** occurs when ProseMirror attempts to access properties before the component lifecycle is fully initialized. This is a common race condition in GrapesJS.

Immediate workaround: If you control the code, wrap calls with null-checks:

if (component && typeof component.method === 'function') {
  // your code
}

Root cause analysis: The ProseMirror doesn't validate state before invoking your method. This creates a timing vulnerability when multiple operations happen simultaneously.

Next steps:

1. Try the null-guard workaround above
2. Update to the latest GrapesJS — many race conditions have been fixed
3. If this persists, share your exact reproduction steps with the team
4. Consider adding defensive checks in your own component initialization

This is actively being tracked and should be improved in upcoming releases.