Corruption archiving .rar files to external drives

Could it be some kind of write-caching issue?

Just checked one of the enclosures and all 4 drives have write-caching disabled ("quick removal" is selected).

I see there are several threads in here with similar issues with copying files to external drives and corruption. None mention archive files in particular. I'm wondering now if non-archive files I've been copying over have also been getting corrupted without me even knowing it. Scary thought. I think I'll be using Teracopy for non-archive files going forward until I can figure out what's happening here as a precaution.

It's weird because I haven't had any archive tests fail if I archive to my internal drive and then copy over to the external, but that takes twice the time. But that suggests that it's not the copying that's an issue - it seems to point specifically to me archiving directly to the external drive, which I've never had a problem with before.

I archived some rar files to one of the external drives today and there was no corruption. It seems totally random when this happens which makes it difficult to track down. I'm still wondering if my USB card is having issues.

I hate the idea of archiving locally and then using Teracopy to copy them over externally because that takes twice the amount of time as just archiving directly to the target drive.