*patpat* I feel your pain, Mark-sf.
The second last time I tried to use Windows Explorer to copy over three folders, which were filled with about 30GB worth of music in total, the Jr. behaved in the most bizarre fashion.
It started transferring files, as one would normally expect. So, I let it continue in the background and went about my business, doing other things. When I checked back about 10 minutes later, I noticed the file transfer was reporting that it was going at a speed that was similar to USB 3.0. "Odd", I thought to myself. I was pretty sure it only had a USB 2.0 connection. Oh well. Just let it go and see what happens.
Once completed, the folders were an utter and total mess, filled with gibberish files, false files sizes, etc.
I had to run CHKDSK to sort it out and eventually just delete it all.
After that, I chucked the thing in a drawer and let it sit there for a week before I tried to transfer files over again. This time, I just moved one folder at a time, and it worked as expected.
So yes. I can completely agree with your assessment of the state of the Jr's firmware, and how it's in a pretty ridiculously poor state for an expensive consumer-grade device. Sure, others will say, "I haven't experienced any problems". And frankly, good for those people. But the point is, those people were lucky. For the prices that AK charges, they need to make certain every possible usage scenario is covered in their firmware. Or at least, as many usage scenarios as is reasonable.
And I don't think, "Copying three folders" is an unreasonable usage scenario.
I intend to give AK one, MAYBE two firmware revisions for the Jr. to get it right. If not, then I'm going to sell it to some other poor schm—er, I mean, an AK aficionado.