Steps to reproduce:

* Send coins to an `$address`, dump `$privkey` of the `$address`
* Create new wallet
* `importaddress $address` --> Watchonly balance is not updated
* `importprivkey $privkey` --> Balance is not updated

Needs a restart to get fixed. See also #11477 
ExternalSigner signer = ExternalSignerScriptPubKeyMan::GetExternalSigner();
        // TODO: add account parameter
        int account = 0;
        UniValue signer_res = signer.GetDescriptors(account);
        if (!signer_res.isObject()) throw std::runtime_error(std::string(__func__) + ": Unexpected result");
        for (bool internal : {false, true}) {
            const UniValue& descriptor_vals = find_value(signer_res, internal ? "internal" : "receive");
            if (!descriptor_vals.isArray()) throw std::runtime_error(std::string(__func__) + ": Unexpected result");
            for (const UniValue& desc_val : descriptor_vals.get_array().getValues()) {
                std::string desc_str = desc_val.getValStr();
                FlatSigningProvider keys;
                std::string desc_error;
                std::unique_ptr<Descriptor> desc = Parse(desc_str, keys, desc_error, false);
                if (desc == nuptr) {
                    throw std::runtime_error(std::string(__func__) + ": Invalid descriptor \"" + desc_str + "\" (" + desc_error + ")");
                }
                if (!desc->GetOutputType()) {
                    continue;
                }
                OutputType t =  *desc->GetOutputType();
                auto spk_manager = std::unique_ptr<ExternalSignerScriptPubKeyMan>(new ExternalSignerScriptPubKeyMan(*this));
                spk_manager->SetupDescriptor(std::move(desc));
                uint256 id = spk_manager->GetID();
                m_spk_managers[id] = std::move(spk_manager);
                AddActiveScriptPubKeyMan(id, t, internal);
            }
        }
    }
}
void CWaet::AddActiveScriptPubKeyMan(uint256 id, OutputType type, bool internal)