Revenue Cloud: Configurator API returns 'A bundle component can belong to only one bundle' intermittently

Cause 1: Configuration instance not saved between configure calls
1. After every successful call to /services/data/v64.0/connect/cpq/configurator/actions/configure, immediately call /services/data/v64.0/connect/cpq/configurator/actions/save-instance with the same contextId before issuing another configure call or invoking Place Sales Transaction.
2. Example save-instance request body: {"contextId": "<the contextId returned by configure>"}.
3. Do not reuse a contextId from a previous transaction across a new configure call. Start a new configure call to obtain a fresh contextId for each configuration session.
4. In Apex callers of PlaceSalesTransaction, wrap configure → save-instance → PST as a single sequential unit; do not parallelize these calls for the same transactionId [Quote.Id / Order.Id].

Cause 2: Duplicate component references in the PST payload
1. In the PST payload, ensure every addedNodes entry has a unique synthetic id (for example, ref_b594ba89_2298_4b6a_bbd7_1dd664f0d1d4). Do not reuse the same id for two components.
2. For each child component, set SalesTrxnItemRelationship.MainItem to the synthetic id of exactly one parent in the same payload. A child must not appear under two MainItem references.
3. When you reuse the output of a Saved Product Configuration as input to PST, regenerate the synthetic ids before submission and verify each ProductRelatedComponent [ProductRelatedComponent.Id] resolves to a single parent in Setup > Object Manager > Product Related Component [ProductRelatedComponent].
4. Set the configurationOptions block explicitly: "configurationInput": "runAndBlockErrors", "configurationOptions": { "validateProductCatalog": true, "validateAmendRenewCancel": true, "executeConfigurationRules": true, "addDefaultConfiguration": true }.

Please find the below detailed article which states which attributes needs to be added.