Root cause: after scale auto-confirm fires submitUse(), the old code called
_cancelScaleAutoConfirm(false) which reset _scaleLastConfirmedGrams to null.
This allowed the scale (still showing the same reading) to start a new 10-second
stability+confirm cycle and trigger a second identical deduction.
JS fix:
- submitUse() now calls _cancelScaleTimersOnly() instead of
_cancelScaleAutoConfirm(false), preserving _scaleLastConfirmedGrams so the
same weight is rejected until the product is removed from the plate.
- _scaleStabilityVal reset to null so a genuinely new weight starts fresh.
- Duplicate API response (result.duplicate) silently ignored in the UI.
PHP fix (server-side safety net):
- useFromInventory() rejects a second 'out' transaction for the same product
within 12 seconds with { success: false, duplicate: true }.
This catches any client-side edge cases regardless of scale timing.
dadaloop82
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