Unless I'm reading it wrong, the documentation for the Bank Reconciliations API is inconsistent with itself.
The text definition says that the transaction_id should be a string, which is generally consistent with Zoho's practices:
The example, which also shows up in the .md files for LLMs, shows that as an integer:
I'm having a hell of a time getting a very simple two-transaction reconciliation to work. Not sure if this is the root cause yet, but the discrepancy needs to be fixed either way.