listdescriptors true fails after importing a 2-of-3 multisig descriptor (prv, pub, pub)

Question

By deafult, in a newly created descriptor wallet that is not watch-only and not empty, listdescriptors true works and gives output.

However, here is a scenario that breaks it:

1. Get a new address in the descriptor wallet.
2. Retrieve its public address (pub1)
3. Create a multisig address with using this public address (pub1) and two others (pub2, pub3)
4. Import the following descriptor into the wallet: sh(multi(priv1,pub2,pub3); I retrieved priv1 from listdescriptors true.
5. Now, if I try listdescriptors true again, an error is returned:

"error": {
  "code": -4,
  "message": "Can't get descriptor string."
}

Is this expected as a result of how I imported a descriptor that mixes xprv and pubkeys, or is it a bug?

---

Note: when importing such a descriptor, I got a warning:

{"success": true, "warnings": ["Not all private keys provided. Some wallet functionality may return unexpected errors"]}