Bad File Format (405)

I have had little success with any type of external drive plugged in via the USB port reading any wav file I chuck at it. I've tried MPC4000 sample packs, z4/8 sample packs, my own wav collections. I've also tried a USB flash drive, a SSD drive and a compact flash drive. Each drive has been formatted using the MPC utility.

When I load a sample with any of the mentioned storage drives I get the dreaded Bad File Format (405). Noting if I save a project with samples recorded from the MPC4000, they load the projects with no issues.

I've read that these can be corrupt files, corrupt sources, etc but each drive can't be corrupt. Two of them (compact flash and USB flash drive) are new , ,and as mentioned formatted using the MPC 4k.

Am I doing something wrong?

If the media is working correctly when written by the MPC, then it‘s probably the PC/Mac writing that spoils the data...
(you may peek file content with a hex editor to detect a pattern)

if all the media (CD-ROM, R/W-CD, USB thumb) you connect to the front USB error, could you try to connect a USB keyboard to see it is not the connection/connector or USB controller who is at fault here?

Can confirm a USB keyboard works fine.

so when you save/load a project made entirely on the MPC you don't have any issues?
only when loading with samples from an "external" source?

and saving/loading on the internal HD works fine?
both 'internal" projects and mixed ones?