Which country are you exporting to? Remember even if the incident occurs outside the UK, you are still in the UK so the Food Safety Act applies to you.
I'd say this is undermining your HACCP plan and there is a need to do different. I'd suggest you look into metal detection or filtration in your process. So for example, if you have filtration very close to the end point, that could be your foreign matter control. Alternatively you could have some kind of throat metal detection I'm guessing? It's more normally used for loose product rather than part frozen liquid but it's worth checking with some of the big suppliers to see if it can be done.
In a former job, we used to export large cheeses which bypassed our packing room. When I arrived at the company, I'd been working there for a couple of weeks and saw one of these cheeses. I said to my manager "how is it metal detected?" After going slightly white, the product was swiftly discontinued.
There isn't a legal requirement for metal detection to be a CCP but with hindsight, would the company regret this? Doesn't it undermine your due diligence?
Barrister "Child X choked on your ice cream after a metal nut was present. I put it to you Tutan that you identified it as a CCP in your procedures, which for the lay person means you've identified it as critical, something which should never be bypassed, but are willing to bypass it for money. Is that correct?"