I was resurrecting a Pi-B for a friend to play with and seems I might have uncovered a bit more info on the external drive mounting issue. I was able to reproduce it every time too. Here's what I did on my x86 system:
1. I boot up my usb thumb drive with LE 11.0.6 test system
2. Plugged in an 8gb separate thumb drive formatted NTFS [System Message confirms mount]
3. From File Manager I copied a small MP4 file to the 8gb thumb drive.
4. I unplug the 8gb drive. Safetly Removed is displayed. Plug it back in a moment later and no mount message.
5. Unplug the drive and message Safetly Removed appears.
6. Plug 8gb drive into Windows system and immediately reports drive error. Scan reports errors repaired.
The error seems to be created only when File Manager writes to the drive and reading has no issues.
I've done this three times with same results. Maybe there is enough info here to chase down this gremlin.
I have the debug log if needed.