When you do a rename operation that makes edits in multiple files, undo does not correctly undo the edits in files other than the active document.

// In a.ts
export function foo() {}

// In b.ts
import { foo }  from './a'
foo();

Rename from the usage of foo() to foo3. Then undo. The code now reports errors on the import because the definition in a.ts is still foo3.

I believe this affects any extension which provides a WorkspaceEdit crossing multiple files.