TPS546D24A: TPS546D24A Three-Phase Stacked Configuration Long-Term Operation Failure

Part Number: TPS546D24A

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This is a three-phase stacked configuration. Test data: 12V input, with each phase outputting 1.2V at 30A. After prolonged operation, the output shuts down automatically; power must be cycled to restore operation, but the fault recurs. The root cause is unclear. Documentation only provides examples for two-phase and four-phase setups. Attached is the current schematic; could you please advise on what might be causing this issue?