Ive done about a dozen ALRs over the years.
Sometimes the gates work, sometimes they dont. There is no real reason for this either, to the extent that I have had the same gate accept the ticket one day, and then reject it the next day!
Ive never had the machine keep my ticket though, so its fine. Just try and use the gates nearest to where the member of staff is for when it fails. and of course theres no consistency with staff either, some just wave it through, others will look at it and be like "ooh, you dont see many of those", whilst others will get all confused, not know what it is, insist you try the gate again etc etc!
Staff on train are varied too. Ive had plenty suggest "it isnt valid on this train", while others are fascinated to see them, and ask how far youve travelled, where else youre going etc, generally interested
As for delay repay, yes you can claim (based on the price of a standard single ticket). last time I claimed, it was refunded within days. Then a week later I got a message stating that I was not entitled to a refund, as the service I was on was not delayed. And then showed the details of a totally different service. I politely replied that I already had my refund thank-you-very-much!
Another time, on a 14 day ALR, there were so many delays and cancellations that I got about half my money back!