Firestore lite: RestConnection RPC [FirebaseError: Request failed with error: undefined]

### [REQUIRED] Describe your environment

* Operating System version: Ubuntu 18.04 (Cloud Functions Node 16)
* Browser version: N/A (Running on Cloud Functions with Node 16)
* Firebase SDK version: 9.19.1
* Firebase Product: firestore/lite

### [REQUIRED] Describe the problem

We recently just tried to switch our production application to use `firestore/lite` instead of the complete Firestore SDK in our Cloud Functions.
Now, every once in a while, Firestore throws errors in this form:

```
@firebase/firestore: Firestore (9.19.1_lite): RestConnection RPC 'BatchGetDocuments' 0x11d7c49f failed with error: [FirebaseError: Request failed with error: undefined]
```

This can happen for read and for write operations, but very very rarely.
We never had such issues before switching to `firestore/lite`. The `undefined` error also makes it impossible to debug.

#### Steps to reproduce:
Use `firestore/lite` in Cloud Functions.