In an LPG depot, a malfunction of safety equipment was noted on the wagon unloading station. The test, carried out during an inspection by the inspection authorities for classified facilities, involved the emergency securing of the rail tanker unloading station. Normally, pressing the button causes various actions including bleeding of the compressed air circuit supplying the turnbuckle, which is a device connecting a clamp attached to the rail to the the bottom valve of the wagon. During a wagon movement, the turnbuckle “popped off” thereby causing tension on the cable and closing the bottom valve. When air is cut off, intentionally or otherwise, the same process occurs in order to isolate the wagon as a safety precaution. On 25.10, several tests carried out by activating the emergency stop on one of the wagons in situ did not lead to the closure of the bottom valve, whereas the compressed air control had worked correctly (releasing the turnbuckle on the rail). The bottom valve of the wagon concerned was of the hydraulic lift type (type less common at this depot). Seemingly possessing greater inertia, it revealed a weakness of the turnbuckle. The tests carried out on the other wagons (raised by compressed air) did not reveal any anomalies (closure in 3 s). After discovering this discrepancy, the inspection authorities for classified facilities asked the operator to check in its other depots in the region, and to carry out the following actions: ask a competent organisation to evaluate the mechanism; implement systematic testing of the turnbuckle before any wagon unloading operations on a temporary basis and before receiving the findings of the expert appraisal; conduct an analysis of the problem encountered; improve the traceability of the tests and the efficiency of the device in place (quarterly frequency sufficient?, preliminary analysis when a new device appears, etc.).