A VeraCrypt volume resides on a device/filesystem that utilizes a wear-leveling mechanism (e.g. a flash-memory SSD or USB flash drive). A copy of (a fragment of) the VeraCrypt volume may remain on the device. Therefore, do not store hidden volumes on such devices/filesystems.

I understand that page is a bit dense, so I’m quoting the relevant text from the above source.

PSA: Veracrypt recommends against using hidden volumes on USB flash drives (source)