64GB SD card corruption?

Your camera firmware likely corrupted your SD card file system when the file system storage reached its capacity limit.

If this is FAT, the file allocation chain is very likely corrupted. FAT is not particularly robust against corruptions.

Subsequent access to the corrupted storage will either work or won’t, based on the details of the particular operation attempted and the particular corruption.

This corruption can be addressed by an update to the camera firmware to not corrupt the file system when at the storage limit, or by avoiding the latent error in the camera firmware by avoidance; by not filling the file system.

For this particular SD card, offload the contents, reformat it, and reload it. Or offload, reformat, and re-use it elsewhere.

More than a few systems and apps do not react graciously at the storage capacity limits. macOS gets decidedly cranky here, as do various MacOS apps.

Another similar mess that can arise here are SD or other storage cards with counterfeit capacity reports. The card presents itself with 64 GB capacity, but actually has some other lower capacity. (Details and Linux tooling)

Ian R. Brown wrote:

I am fairly certain there is nothing wrong with the card.

The problem was with the old reader - a USB 3.0 Kingston MobileLite G3.

A cheapo (£1 from China) reader I had lying around saved the day but it took 1h 45m to transfer the 62GB the card contained so it looks like I need a new reader.

Just out of curiosity, how long should it take to transfer 60+GB from a U3 card to the computer?

CORRECTION: This card was a U1

There are several variables. The cards themselves are not all the same - in fact there are several classes according to card characteristics:

https://www.sdcard.org/developers/sd-standard-overview/speed-class/

And, of course, there are very different readers. Many may support only USB2, so even it is a case of what the limiting factor is, the card or the reader.

For serious work, I'd recommend offloading the camera cards to a local disk file using a checksummed copy method, then import to FCP from there.

If you import the files from a card using FCP, it does not do a checksummed copy. Normally, that's OK, but occasionally you may encounter a problem, and the consequences can be significant.

My team uses the product from Hedge called "Offshoot" which is designed for this. But you could also use Carbon Copy, which although designed for backups, can also be used for checksummed offloads.

All Macs have the built-in command-line tool rsync which has optional checksumming.

Probably the least expensive paid Mac GUI tool is TeraCopy, which is in the App Store. It has some mediocre reviews, but I've never tested it myself.

There are some free ones (which I also have not used): FreeFileSync, and several through Homebrew such as muCommander.

If you have Resolve (even the free version), there is a built-in file "clone" tool that's like a lightweight version of Hedge Offshoot. It is designed for offloading files. Search Youtube for Resolve clone tool backup to see tutorials.

Instead of relying on the SD cards, I'd recommend you make full copies of them. Hard drives and especially SSD are much more robust than SD cards.

Since the SD card is giving trouble, I'd make sure that everything in it is copied at least to two different locations, and then reformat the card in the camera; then do some test filming to see if the card is behaving properly. If it still gives issues, discard it (pun intended :-)).

Never let an SD card fully fill up like that. Keep closer watch on them.

There's also ShotPut Pro which we've used for a while now to offload camera cards. Same subscription model as Offshoot I believe.