Constantly fails to export some photos

[#1]

Since the last update, almost every time I export photos to jpg, it inevitably fails to write a random number of them- then I have to keep doing it until they all export. Export 200, 50 fail. Export 50, 21 fail. and so on. No issues with disk permissions from what I can see.

I'm on a 2019 iMac exporting from external 10TB to the internal Fusion drive, into a Dropbox folder. Could it be a change in the Dropbox app, if not Adobe? Pausing syncing does not fix the problem.

[#2]

Since the last update, almost every time I export photos to jpg, it inevitably fails to write a random number of them- then I have to keep doing it until they all export. Export 200, 50 fail. Export 50, 21 fail. and so on. No issues with disk permissions from what I can see.

I'm on a 2019 iMac exporting from external 10TB to the internal Fusion drive, into a Dropbox folder. Could it be a change in the Dropbox app, if not Adobe? Pausing syncing does not fix the problem.

[#3]

Do you get an error message? If so, what is the exact unedited word-for-word error message?

How much free space is left on the internal Fusion drive? (What is an internal Fusion drive?)

Have you tried the simple test of exporting to a different drive and/or a different folder to see if the problem goes away?

[#4]

Seems to have worked when exporting to the same external the raws are on.

The internal drive has plenty of space left, 82gb/2TB (sure, could use a cleanup, but it's by no means critically low) 

Fusion drives are a Mac thing in their desktops where they contain both an SSD and HDD and it automatically moves files between them for efficiency. 

The error message was simply 'x photos failed to export' and gives the option to show in library, where it creates a 'Photos That Failed to Export' section under 'previous import'

[#5]

"Seems to have worked when exporting to the same external the raws are on."

So, we have determined that there is some problem exporting to the Fusion drive, it may be Dropbox, it may be the drive itself. You will need to run diagnostics on this drive to make sure it is functioning properly.

[#6]

So it appears to be a 'low' space issue on the drive- I cleared out a good amount of files and freed up like 300gb and it exports fine now. 

I know it's not good to stuff drives to their max, but I think it's ridiculous that a drive would start functioning incorrectly with 80 whole gigabytes of free space - that's 25% free space.

[#7]

It’s 4.1%