Copying from an MTP device (Samsung Note 10.1 and Samsung Galaxy S5) only copies some of the files. I can drill down and copy individual files, but copying folders does not always copy the folder's contents. (Yes, mtp_enable is true.) Is there something I need to do to make DO copy all files in all subfolders?
There are some improvements to MTP handling in the latest Opus beta, although they are not guaranteed to help as some of the problems are in the Android and Windows MTP stacks rather than Opus itself.
If any Android system updates are available for the devices, those have been known to help with Samsung's versions of Android in some cases. (Samsung's versions of Android have been particularly problematic when it comes to MTP.)
Failing all of that, switching to mtp_enable = false may help, as that will make Opus use the Windows shell to handle MTP folders.