can't access folder on functional external drive

I have an external USB 3.0 drive with a folder that won't show it's contents. Here's the info:

- I'm running 10.13.3

- the external drive is a 2.5" USB powered APFS (all of my other external drives are Mac OS Extended Journaled).

- the drive is directly attached

- the problem occurred before I could Carbon Copy Cloner the contents to a backup location (all files outside of this folder were successfully copied over

- the drive mounts successfully

- I've run first aid multiple times and it completes successfully

- the folder of concern is the only folder on the drive

- I can add files to the drive (outside of the folder) and access them successfully

- moving, copying, duplicating this folder causes finder to freeze and I usually have to restart the Mac

- this is the only drive not recognizable by DiskWarrior disk repair software

- any ideas as to how I can access the folder contents?

- I don't believe a nondestructive reformat (preferably back to extended journaled) is possible in Mac OS, but please let me know if it is

I've used Macs for 7 years now and know my way around them very well. I've never heard of this sort of issue before. I can't find this issue on youtube.