Our former mechanic Bob can more once told me that if you yank on it and you stay hook and you check to see The lever has completely retracted then you've done your job for the pre trip and should have no expectation that the 5th will fail. If the lead trailer should come detached from the 5th wheel that's a mechanical failure not a driver failure. I know of 2 incidents when this happened at my 17 years at 050 and both times they sent the 5th wheel to Fort Smith for inspection and both times they found excessive wear. I don't remember the outcome but I don't think the driver was held responsible