5 years have passed, but the problem is still relevant (Xcode 12.4). As a temporary solution, Xcode has to be closed completely. After that, the project is re-indexed and there is enough memory to rename 2-3 classes, after which the action has to be repeated.

I also faced such a problem for the SwiftMessages library, which is simply present in the local SPM framework. Appeared only on XCode 13 beta 3, before that on XCode 12 everything works fine.

Same problem. Were you able to find a solution?