Why?

Don't know if it's connected but I'd read Sandisk ones are no good in dashcams particularly because of the way they handle sectors that die, one goes and the whole card becomes read only rather than it just marking it not to be used and carrying on like other cards.

I had similar issues a number of times with Sandisk cards, particularly in Samsung devices it seems. Never had problems with Samsung cards in any devices.j

Yeah I had issues with 2 sandisc microSD cards, one of them was actually the 32GB version of this card (both bought from credible retailers so not some lame ebay fake)
When I contacted them they wanted me to send it all the way too the chech republic (no UK returns address) at a cost of about £8 which made the RMA pretty economically pointless.
I won't touch sandisc stuff now, the lack of a UK returns address makes their lifetime/extended warranties an expensive and somewhat disingenuous selling point. I buy Kingston & Samsung memory now, no issues :-)

I wonder how many more SanDisks are sold than other brands? They appear to be ubiquitous.
It's like my local council tip telling me they'll see my Dyson back in a couple of weeks when I disposed of the box it came in - "We get loads of them."....Hmm. Why could that be then?

I'd suggest this guy maybe had other issues - either the device he was putting it in or how he was reading/writing data to it. Who knows...I've had loads of SDcards and they've been fine.

SanDisk are one of the most counterfeited sd cards available and I believe most problems people have are after buying a rip off one and not even realising.