Only once, ever, at a ticket gate - and that was a really odd case where my FOSS▸ had failed to work the gate, I was the only passenger around, and the bloke on the gate insisted on taking a careful look at my ticket and punching a hole in it having got his punch out from the cupboard.
This happened to me once with my FOSS, at Southampton Central. Where was yours, as I wonder whether it was something specific to that station?
The woman at the barrier took a lot of time checking my ticket, asking where I was going and generally questioning it, and insisted on punching it too, and I only just made it onto the platform in time to catch my train.
Mine was Chippenham ... and I found myself wondering if punching a hole in a ticket these days is a way of signalling to other staff "awkward customer". Staff are usually excellent, but this was the exception. I do recall a more thorough check of my FOSS that usual at Southampton Central too - same person perhaps - but then utterly helpful there on other occasions.
The FOSS ticket is a bargain if you want to do what it allows, and I wonder if s minority of staff resent the really good price you've got your travel at. I've found the same attitude on occasions with my Interrail pass.
The FOSS ticket is certainly a bargain. At Southampton Central, platform 4, I had the impression that the woman at the barrier had never actually seen a FOSS ticket before, and didn't really believe I could have a ticket that allowed me to travel that far. She held onto it for some minutes asking me questions, and didn't seem any the wiser at the end of the time.
At most stations I found the FOSS ticket wouldn't open the barriers, which was very frustrating, as at a few stations it did (so presumably could do so anywhere).