It is possible that the range is bigger than they thought, in which case if I felt this way I'd be 'discussing' this with Nikon and suggesting that as they have a known shutter issue that they fix it as a goodwill gesture. But as I mentioned before the shutter recall was for banding, not shutter failure so I'm not exactly sure where you stand tbh.
Nikon's weak point does seem to be shutters, if you google you will see that numerous Nikon cameras have had shutter faults and err messages so it's not just the D750. I think the D750 has been highlighted as Nikon admitted a fault with the shutter, but as I've said a couple of times now that was due to banding. AFAIK they've not admitted a fault or recall due to err messages and/or shutter failures. Those that have had these messages and failures and also fell within the range of cameras with the banding issue have had their shutters replaced as part of the recall.
How old is your camera, I've forgotten? Warranties aren't set in stone per se and items should be fit for purpose and should last a 'reasonable' amount of time. If something fails within a period of time that it shouldn't you are sometimes entitled to a repair at no cost to yourself. I can't remember if this is with the store you bought it from, or the manufacturer but my instinct tells me that it's with the store. Citizens Advice will be able to help you further with this.
I'm not defending Nikon's inability to make robust shutters, but from Nikon's standpoint it is just an unfortunate fault rather than being related to the known shutter issue and will not see it as having more cameras than they were aware of having the known shutter fault. As you can see from this, there is no mention of err messages, lockups or failures.
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Now if you, or someone else could prove that the shutter failures and the banding/shading issue are/were related that would be a different matter and I would assume that you would be well within your right to a replacement. That being said, I would still argue that the camera hasn't lasted anywhere near the life-expectancy (the shutter is rated to 150,000 actuations) and ask for it to be replaced under goodwill/under your rights as a consumer. Again, with the latter point Citizens Advice will be able to help you further. Certainly worth pursuing imo, £190 is a lot to fork out.
So either it's miscommunicating with the camera, won't hold full charge anymore, or miscommunicating with the charger and saying it's full when it's not.
